Abstract: DNA damage induced by aminophenols in carp (Cyprinus caprio) kidney cells in vivo was studied using comet assay or the alkaline single cell gel electrophoresis (SCGE). Carps were treated with different concentrations of aminophenols and the assay was performed on kidney cells after 72h. Four different parameters, including AU, TDNA, MT and MOT, were gained for comparison and similar results were displayed. A significant increase (P<0.05; P<0.01) in DNA damage was observed at all concentrations with three test substances when compared with solvent control. The DNA damage scorings showed a dose-related increase. The results showed that the genotoxicity of the three tested substances varied greatly. Maybe the reason was that the genotoxicity was partly related to the different structures. The study revealed that the comet assay is an adequate and promising test system for environmental biomonitoring.