The Visual C++ runtime library now detects incorrect iterator use and will assert and display a dialog box at run time. To enable debug iterator support, a program must be compiled with a debug version of a C run time library (see C Run-Time Libraries for more information). See Checked Iterators for more information on using iterators. The C++ standard describes which member functions cause iterators to a container to become invalid. Two examples are: Erasing an element from a container causes iterators to the element to become invalid.   Increasing the size of a vector (push or insert) causes iterators into the vector container become invalid. Here, VC++ Software Engineer Stephan T. Lavavej digs into the details of STL Iterator Debugging including its implementation, usage scenarios and interesting facts you may not find anywhere else (Channel 9 goodness). Stephan is known as STL (this is his name’s acronym, by coincidence or perhaps it's simply prophetic since Stephan is a passionate advocate for STL, as you will no doubt understand after watching and listening to this conversation). Stephan also dives a bit into Secure SCL, which is part of the VC++ Safe Libraries. Stephan does not possess a marketing bone in his body as you can tell by his commentary that's weaved into his informal presentation of advanced topics. I love this. He speaks his mind freely, though with fairness, and that's the only way to be. Enjoy!