Dietary consumption of green vegetables has been associated with protection against mutagenic and clastogenic activity of genotoxicants. Chlorophyll, being present in all green plants, had earlier been suggested to be the principal factor involved. Mice were administered (i) crude aqueous extract of leaf of Indian spinach, Beto vulgaris L. var. benghalensis Hort., and equivalent amounts of (ii) chlorophyll extracted from the leaf; (iii) purified chlorophyll, (iv) chlorophyllin, a sodium-copper derivative of chlorophyll; daily for 7 days. On day 7, one set of mice from each treatment was administered potassium dichromate - a known metallic clastogen. The mice were sacrificed after 24 hours. Chromosome preparations were made from bone marrow following the usual colchicine-air dry-Giemsa schedule. The cytogenetic endpoints scored were chromosomal aberrations and damaged cells. Crude leaf extract and chlorophyllin were nonclastogenic and reduced the clastogenic effects of potassium dichromate to the control distilled water level. Chlorophyll alone, whether extracted from the leaf or obtained in commercially purified form, was clastogenic and could reduce the effects of the chromium salt only to its own level. The protective action of the crude leaf extract may be attributed to the total effect of the interaction between the different components within the leaf extract, in which the clastogenicity of chlorophyll had been neutralized.