For the control of sterilisation processes in autoclaves several biological indicators were examined and compared with native spore samples. The biological indicators were STERIKON (Merck, Darmstadt), KILIT (BBL, USA); the ampulated native spore samples came from Mainz and Berlin, furthermore Bac. subtilis was used on arenaceous quartz. To receive more accurate results and better possibilities for standardization, indicators were not tested in autoclaves but in ultrathermostates. The effect of heat on the viability of ampulated test spores was ascertained by the count of colony formating units on count plates. With two of the tested indicators, KILIT and STERIKON, success of the germicidal process can also be seen by the change of color of the contents of the ampules. Investigations showed ampulated wet spore samples to be totally inefficient, because of their low resistance level, but also suspensios of Bac. subtilis did not meet requirements. Tests of KILIT indicated equally unsatisfactory low levels of heat resistance. Only KTERIKON met the requirements and equalled native spore samples. Since the producer lowered the heat resistance, which was too high initially, by reducing the sowing of spores to 10(2)-10(3) per ml medium of the ampules, the germicidal curve became almost ideal. It has to be mentioned that STERIKON-ampules can only be recommended to ampule-producing-industries. For the control of medicaments in ampules a replacement of native spore samples by STERIKON will only be possible, after the producer has standardized the optimal heat resistance and prevented its decrease while being stored. At present native spore samples are still indispensable - also because they can be widely employed.