diff --git a/ClosedXML/Excel/XLWorkbook_Save.cs b/ClosedXML/Excel/XLWorkbook_Save.cs
index 8f47b30..74f0f52 100644
--- a/ClosedXML/Excel/XLWorkbook_Save.cs
+++ b/ClosedXML/Excel/XLWorkbook_Save.cs
@@ -5189,21 +5189,35 @@
 
             #region RowBreaks
 
-            if (!worksheetPart.Worksheet.Elements<RowBreaks>().Any())
-            {
-                var previousElement = cm.GetPreviousElementFor(XLWSContentManager.XLWSContents.RowBreaks);
-                worksheetPart.Worksheet.InsertAfter(new RowBreaks(), previousElement);
-            }
-
-            var rowBreaks = worksheetPart.Worksheet.Elements<RowBreaks>().First();
-
             var rowBreakCount = xlWorksheet.PageSetup.RowBreaks.Count;
             if (rowBreakCount > 0)
             {
+                if (!worksheetPart.Worksheet.Elements<RowBreaks>().Any())
+                {
+                    var previousElement = cm.GetPreviousElementFor(XLWSContentManager.XLWSContents.RowBreaks);
+                    worksheetPart.Worksheet.InsertAfter(new RowBreaks(), previousElement);
+                }
+
+                var rowBreaks = worksheetPart.Worksheet.Elements<RowBreaks>().First();
+
+                var existingBreaks = rowBreaks.ChildElements.OfType<Break>();
+                var rowBreaksToDelete = existingBreaks
+                    .Where(rb => !rb.Id.HasValue ||
+                                 !xlWorksheet.PageSetup.RowBreaks.Contains((int)rb.Id.Value))
+                    .ToList();
+
+                foreach (var rb in rowBreaksToDelete)
+                {
+                    rowBreaks.RemoveChild(rb);
+                }
+
+                var rowBreaksToAdd = xlWorksheet.PageSetup.RowBreaks
+                    .Where(xlRb => !existingBreaks.Any(rb => rb.Id.HasValue && rb.Id.Value == xlRb));
+
                 rowBreaks.Count = (UInt32)rowBreakCount;
                 rowBreaks.ManualBreakCount = (UInt32)rowBreakCount;
                 var lastRowNum = (UInt32)xlWorksheet.RangeAddress.LastAddress.RowNumber;
-                foreach (var break1 in xlWorksheet.PageSetup.RowBreaks.Select(rb => new Break
+                foreach (var break1 in rowBreaksToAdd.Select(rb => new Break
                 {
                     Id = (UInt32)rb,
                     Max = lastRowNum,
@@ -5222,21 +5236,35 @@
 
             #region ColumnBreaks
 
-            if (!worksheetPart.Worksheet.Elements<ColumnBreaks>().Any())
-            {
-                var previousElement = cm.GetPreviousElementFor(XLWSContentManager.XLWSContents.ColumnBreaks);
-                worksheetPart.Worksheet.InsertAfter(new ColumnBreaks(), previousElement);
-            }
-
-            var columnBreaks = worksheetPart.Worksheet.Elements<ColumnBreaks>().First();
-
             var columnBreakCount = xlWorksheet.PageSetup.ColumnBreaks.Count;
             if (columnBreakCount > 0)
             {
+                if (!worksheetPart.Worksheet.Elements<ColumnBreaks>().Any())
+                {
+                    var previousElement = cm.GetPreviousElementFor(XLWSContentManager.XLWSContents.ColumnBreaks);
+                    worksheetPart.Worksheet.InsertAfter(new ColumnBreaks(), previousElement);
+                }
+
+                var columnBreaks = worksheetPart.Worksheet.Elements<ColumnBreaks>().First();
+
+                var existingBreaks = columnBreaks.ChildElements.OfType<Break>();
+                var columnBreaksToDelete = existingBreaks
+                    .Where(cb => !cb.Id.HasValue ||
+                                 !xlWorksheet.PageSetup.ColumnBreaks.Contains((int)cb.Id.Value))
+                    .ToList();
+
+                foreach (var rb in columnBreaksToDelete)
+                {
+                    columnBreaks.RemoveChild(rb);
+                }
+
+                var columnBreaksToAdd = xlWorksheet.PageSetup.ColumnBreaks
+                    .Where(xlCb => !existingBreaks.Any(cb => cb.Id.HasValue && cb.Id.Value == xlCb));
+
                 columnBreaks.Count = (UInt32)columnBreakCount;
                 columnBreaks.ManualBreakCount = (UInt32)columnBreakCount;
                 var maxColumnNumber = (UInt32)xlWorksheet.RangeAddress.LastAddress.ColumnNumber;
-                foreach (var break1 in xlWorksheet.PageSetup.ColumnBreaks.Select(cb => new Break
+                foreach (var break1 in columnBreaksToAdd.Select(cb => new Break
                 {
                     Id = (UInt32)cb,
                     Max = maxColumnNumber,
diff --git a/ClosedXML_Tests/Excel/Saving/SavingTests.cs b/ClosedXML_Tests/Excel/Saving/SavingTests.cs
index 2dc3f2f..d17ab21 100644
--- a/ClosedXML_Tests/Excel/Saving/SavingTests.cs
+++ b/ClosedXML_Tests/Excel/Saving/SavingTests.cs
@@ -191,6 +191,32 @@
             Assert.Throws(typeof(UnauthorizedAccessException), saveAs);
         }
 
+        [Test]
+        public void PageBreaksDontDuplicateAtSaving()
+        {
+            // https://github.com/ClosedXML/ClosedXML/issues/666
+
+            using (var ms = new MemoryStream())
+            {
+                using (var wb1 = new XLWorkbook())
+                {
+                    var ws = wb1.Worksheets.Add("Page Breaks");
+                    ws.PageSetup.PrintAreas.Add("A1:D5");
+                    ws.PageSetup.AddHorizontalPageBreak(2);
+                    ws.PageSetup.AddVerticalPageBreak(2);
+                    wb1.SaveAs(ms);
+                    wb1.Save();
+                }
+                using (var wb2 = new XLWorkbook(ms))
+                {
+                    var ws = wb2.Worksheets.First();
+
+                    Assert.AreEqual(1, ws.PageSetup.ColumnBreaks.Count);
+                    Assert.AreEqual(1, ws.PageSetup.RowBreaks.Count);
+                }
+            }
+        }
+
 
         [TearDown]
         public void DeleteTempFiles()
diff --git a/ClosedXML_Tests/Resource/Examples/PageSetup/Sheets.xlsx b/ClosedXML_Tests/Resource/Examples/PageSetup/Sheets.xlsx
index f91eecc..2ac5d1d 100644
--- a/ClosedXML_Tests/Resource/Examples/PageSetup/Sheets.xlsx
+++ b/ClosedXML_Tests/Resource/Examples/PageSetup/Sheets.xlsx
Binary files differ