Chloroform does not induce gene mutations in the HGPRT-Test with V79 Chinese hamster cells, either in the presence or in the absence of a metabolic activation system, under the experimental conditions described (Report: Hoechst AG No. 87.0692 of July 3, 1987). Chloroform was examined for chromosomal aberrations in bone marrow cells from Chinese hamsters in two independent in-vivo tests. In the first test, bone marrow metaphases were studied at 6, 24 and 48 hours after the administration of 40, 120 and 400 mg/kg. At 6 and 24 hours there was a slight, statistically significant increase in the aberration rate in the 400 mg/kg group. This was, however, within the range of negative control values from previous studies. In addition to this, there were isolated cases of marked DNA damage (chromosomal disintegration, chromosomal exchange figures) at dosages of 120 and 400 mg/kg. Therefore, a second study was carried out with the doses in question, i.e. 120 and 400 mg/kg. The evaluation of the results confirmed to a great extent the findings of the first study, i.e. there was also a slight significant increase in the aberration rate, which was not dose-dependent. There were also isolated occurrences of marked chromosomal damage.