In this study, respirometric toxicity experiments were conducted to monitor the biological treatability of wastewater generated from a medical waste sterilization plant (MWSP). Experiments, performed using samples from the Kayseri MWSP and conducted for periods of 30 and 180 min, were repeated after being applied to chemical treatment. According to the results, it was seen that untreated wastewater with 2590 mg/L of chemical oxygen demand (COD) and a dilution of 30% inhibited the activated sludge microorganisms by 50%. In a similar way, untreated wastewater with 70% diluted COD will inhibit activated sludge microorganisms by 20%, but wastewater with 90 mg/L of COD did not inhibit them. Also, a chemical coagulation process was applied to the sterilization plant wastewater. As a result, it was shown that oxygen depletion rate of wastewater was negative, and the wastewater had no inhibitive impact on activated sludge microorganisms. Thus, it was concluded that the wastewater generated from the sterilization plant should be pre-treated to enable its biological treatment. These results help resolving the issue that medical MWSPs do not yet have standardized limits.