Abstract: A system for monitoring, testing, auditing and controlling vending machines is disclosed.The system includes a counter attached to the vending machine, and a microprocessor controlled, portable, keyboard operated, collection unit adapted to serve a number of vending machines by accessing and interrogation of the counter. The portable collection unit also is adapted to load a program into the counter, input instructions, data and code changes to the counter and, upon interrogation of the counter, receives various types of output information from the counter.The counter performs functions which include: coin transactions, code validations, inventory control, product and price changes, service and transaction time checks, dispensing, machine diagnostics, temperature control, etc.