Abstract: An apparatus for accounting for surgical instruments dispensed into and withdrawn from the surgical operating environment to avoid leaving instruments in the environment comprises a plurality of instrument bearing compartments mounted on a base, a stand for storing surgical instruments after use, and a digital computer programmed to receive signals both from the compartments as a sterile instrument is dispensed and from the stand when a used instrument is stored thereon, convert the signals to numbers of instruments dispensed and stored, subtract the latter number from the former and display the difference. A non-zero different means an instrument remains in the operating environment and must be visually accounted for by operating room staff. The signal from the compartments is preferably generated an interruption of beam of light carried by fiber optic filaments when an instrument is dispensed from a compartment.