Introduction: Enrofloxacin is the most used fluoroquinolone to treat infections in animals. At the same time, fluoroquinolones are among those antimicrobial chemotherapeutics, which are frequently detected in the environment at relatively high concentrations ranging from ng l−1 to µg l−1. Moreover, their accumulation, toxicity and the resistance of pathogenic microorganisms are of major concern. The present study was performed to determine the cytotoxic effects of enrofloxacin and its biotransformation in an in vitro study using human HepG2 cells.