The article discusses the occurrence of selected cytostatic drugs in the aquatic environment. The authors start with a preliminary introduction to the characteristics of the most commonly used cytostatic drugs. Then, based on the review of the literature they show that such drugs occur in small amounts in an aqueous medium and that there is no reliable research data on the long-term exposure of aquatic organisms to cytostatics. Until now, the studies on the stability of some cytostatics showed that these compounds were extremely stable, not only in natural waters, but also at wastewater treatment plants (WWTPs). In spite of the advanced treatment technologies used at wastewater treatment plants, cytostatics pass relatively easily through the treatment line and end up in surface waters, thus posing a threat to water quality.