A system and method for monitoring the performance of a computer system by dynamically interposing an instrumented trap table. A base address of a trap table, which may be contained in a trap base address register, may be changed to indicate an instrumented trap table. An instrumented trap table may gather a variety of statistics, including the type of trap and an entry timestamp. An instrumented trap table may then call a non-instrumented trap table to process the trap. A non-instrumented trap table may pass control back to the instrumented trap table to collect further statistics, for example an exit timestamp. An instrumented trap table may then return process flow to the calling routing. In this manner, useful performance statistics may be gathered while trap events are processed by regular, optimized software.