Two artificial sweeteners, cyclamate and saccharin, were studied as to their effect on the chromosomes of Chinese hamster cells in vitro. An incidence of chromosome breaks and gaps, significantly increased over the control level, was found in the treated experimental groups. A certain dose relationship of the disturbances induced was indicated. The distribution over the karyotype of the aberrations was nonrandom and the pattern of breaks and gaps in the treated groups coincided largely with that in the controls.