Recording and replaying computer programs includes detecting whether a race condition exists among multiple threads of a multithreaded application program. In an embodiment, detecting race conditions comprises detecting and preventing an operation of a first thread of an application program to read or write a computer memory, wherein the application program executes a plurality of threads; storing an exception point representing a current location in an execution path of the application program; allowing the operation to read or write the memory; creating and storing a record identifying the memory, the first thread, and an index value for a location in the execution path; and determining, based on the record and a plurality of other similar records, whether a race condition exists at the exception point for the first thread and one or more other threads in the plurality of the threads.