Young male CBA/LacStoRap mice were exposed for two hours to volatile components of native or dialyzed urine (VC or VC(d), respectively) of mature males of the same line. To estimate the effects of VC and VC(d) on bone marrow cells, cytogenetic analysis of mitotic disturbances in anaphase-telophase cells was performed. The overall-frequency of mitotic disturbances in VC-treated mice became significantly higher 24 and 48 h after exposure but returned to the initial level 72 h after exposure (P < 0.05). Similar effects were observed after 24 h in mice exposed to VC(d). These results suggest that VC and VC(d) are capable of disturbing the stability of genetic processes in proliferating bone marrow cells. Evidence was also obtained that these components are associated with major urinary proteins. The significance and possible mechanisms of effects observed in the study are discussed.