diff --git a/ApplicationCode/Commands/SummaryPlotCommands/RicNewDerivedEnsembleFeature.cpp b/ApplicationCode/Commands/SummaryPlotCommands/RicNewDerivedEnsembleFeature.cpp
index c1ad462415..ffa32e1e06 100644
--- a/ApplicationCode/Commands/SummaryPlotCommands/RicNewDerivedEnsembleFeature.cpp
+++ b/ApplicationCode/Commands/SummaryPlotCommands/RicNewDerivedEnsembleFeature.cpp
@@ -29,12 +29,37 @@
 #include "cafSelectionManagerTools.h"
 
 #include <QAction>
+#include <QMessageBox>
 
 #include <memory>
 
 
 CAF_CMD_SOURCE_INIT(RicNewDerivedEnsembleFeature, "RicNewDerivedEnsembleFeature");
 
+//--------------------------------------------------------------------------------------------------
+/// 
+//--------------------------------------------------------------------------------------------------
+void RicNewDerivedEnsembleFeature::showWarningDialog()
+{
+    QMessageBox::warning(nullptr, "Ensemble Matching", "None of the cases in the ensembles match");
+}
+
+//--------------------------------------------------------------------------------------------------
+/// 
+//--------------------------------------------------------------------------------------------------
+bool RicNewDerivedEnsembleFeature::showWarningDialogWithQuestion()
+{
+    QMessageBox msgBox;
+    msgBox.setIcon(QMessageBox::Question);
+    msgBox.setWindowTitle("Ensemble Matching");
+    msgBox.setText("None of the cases in the ensembles match");
+    msgBox.setInformativeText("Do you want to keep the derived ensemble?");
+    msgBox.setStandardButtons(QMessageBox::Yes | QMessageBox::No);
+
+    int ret = msgBox.exec();
+    return ret == QMessageBox::Yes;
+}
+
 //--------------------------------------------------------------------------------------------------
 /// 
 //--------------------------------------------------------------------------------------------------
@@ -67,6 +92,14 @@ void RicNewDerivedEnsembleFeature::onActionTriggered(bool isChecked)
             {
                 newEnsemble->setEnsemble2(ensembles[1]);
                 newEnsemble->updateDerivedEnsembleCases();
+
+                if (newEnsemble->allSummaryCases().empty())
+                {
+                    if(!showWarningDialogWithQuestion())
+                    {
+                        mainColl->removeCaseCollection(newEnsemble);
+                    }
+                }
             }
         }
         
diff --git a/ApplicationCode/Commands/SummaryPlotCommands/RicNewDerivedEnsembleFeature.h b/ApplicationCode/Commands/SummaryPlotCommands/RicNewDerivedEnsembleFeature.h
index 2633e24cef..847d091234 100644
--- a/ApplicationCode/Commands/SummaryPlotCommands/RicNewDerivedEnsembleFeature.h
+++ b/ApplicationCode/Commands/SummaryPlotCommands/RicNewDerivedEnsembleFeature.h
@@ -31,6 +31,10 @@ class RicNewDerivedEnsembleFeature : public caf::CmdFeature
 {
     CAF_CMD_HEADER_INIT;
 
+public:
+    static void showWarningDialog();
+    static bool showWarningDialogWithQuestion();
+
 protected:
     // Overrides
     virtual bool isCommandEnabled();
diff --git a/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.cpp b/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.cpp
index 8b813d3813..0ca1e24e29 100644
--- a/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.cpp
+++ b/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.cpp
@@ -19,6 +19,8 @@
 #include "RiaApplication.h"
 #include "RiaTimeHistoryCurveMerger.h"
 
+#include "SummaryPlotCommands/RicNewDerivedEnsembleFeature.h"
+
 #include "RimDerivedEnsembleCaseCollection.h"
 #include "RimDerivedEnsembleCase.h"
 #include "RimProject.h"
@@ -66,7 +68,7 @@ RimDerivedEnsembleCaseCollection::RimDerivedEnsembleCaseCollection()
     m_swapEnsemblesButton.uiCapability()->setUiLabelPosition(caf::PdmUiItemInfo::HIDDEN);
     m_swapEnsemblesButton.xmlCapability()->disableIO();
 
-    CAF_PDM_InitField(&m_caseCount, "CaseCount", 0, "Number of Cases", "", "", "");
+    CAF_PDM_InitField(&m_caseCount, "CaseCount", QString(""), "Matching Cases", "", "", "");
     m_caseCount.uiCapability()->setUiReadOnly(true);
 
     // Do not show child cases
@@ -207,7 +209,10 @@ QList<caf::PdmOptionItemInfo> RimDerivedEnsembleCaseCollection::calculateValueOp
     }
     else if (fieldNeedingOptions == &m_caseCount)
     {
-        m_caseCount = (int)m_cases.size();
+        size_t caseCount1 = m_ensemble1 ? m_ensemble1->allSummaryCases().size() : 0;
+        size_t caseCount2 = m_ensemble2 ? m_ensemble2->allSummaryCases().size() : 0;
+
+        m_caseCount = QString("%1 / %2").arg((int)m_cases.size()).arg(std::max(caseCount1, caseCount2));
     }
     return options;
 }
@@ -236,16 +241,19 @@ void RimDerivedEnsembleCaseCollection::fieldChangedByUi(const caf::PdmFieldHandl
     bool doUpdate = false;
     bool doUpdateCases = false;
     bool doClearAllData = false;
+    bool doShowDialog = false;
 
     if (changedField == &m_ensemble1 || changedField == &m_ensemble2)
     {
         doUpdate = true;
         doUpdateCases = true;
+        doShowDialog = true;
     }
     else if (changedField == &m_operator)
     {
         doUpdate = true;
         doUpdateCases = true;
+        doShowDialog = false;
     }
     else if (changedField == &m_swapEnsemblesButton)
     {
@@ -256,17 +264,22 @@ void RimDerivedEnsembleCaseCollection::fieldChangedByUi(const caf::PdmFieldHandl
 
         doUpdate = true;
         doUpdateCases = true;
+        doShowDialog = false;
     }
 
     if (doUpdate)
     {
         updateAutoName();
-        //if (doClearAllData) clearAllData();
 
         if (doUpdateCases)
         {
             updateDerivedEnsembleCases();
             updateConnectedEditors();
+
+            if (doShowDialog && m_ensemble1 != nullptr && m_ensemble2 != nullptr && allSummaryCases().empty())
+            {
+                RicNewDerivedEnsembleFeature::showWarningDialog();
+            }
         }
 
         updateReferringCurveSets();
diff --git a/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.h b/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.h
index 5913cd1d75..6e76f8c019 100644
--- a/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.h
+++ b/ApplicationCode/ProjectDataModel/Summary/RimDerivedEnsembleCaseCollection.h
@@ -81,5 +81,5 @@ private:
     caf::PdmPtrField<RimSummaryCaseCollection*>             m_ensemble2;
     caf::PdmField<caf::AppEnum<DerivedEnsembleOperator>>    m_operator;
     caf::PdmField<bool>                                     m_swapEnsemblesButton;
-    caf::PdmField<int>                                      m_caseCount;
+    caf::PdmField<QString>                                  m_caseCount;
 };