Filter-paper strips saturated with Bacillus stearothermophilus spores were prepared and then stored for up to 1470 days. The strips were used to measure sport activation time and death kinetics in two systems : a serum bottle/oil bath combination, and glassine packages in a gravity autoclave. The data collected were analyzed primarily by analysis of variance and thr interaction or spore storage time, processing temperature, inertial time and exposure time was determined.