The Swiss Center for Quality Control organizes external quality assessment schemes for medical laboratories as well as biological monitoring of the sterilization process for autoclaves. Over the period from 2008 to 2012, 209 dental offices performed 4,709 sterilizations of biological indicators strips covered by Geobacillus stearothermophilus spores. The median number of sterilizations per participant was 20. Steam autoclaves obtained better results than the Chemiclave. It turned out that 99 strips (2.1%) failed to be properly sterilized, and that 61 participants (29.2%) experienced one or more sterilization failures. In addition, there was no performance improvement over time.