The alkaline comet assay (single cell gel electrophoresis assay) is a sensitive method for the detection of DNA damage. This paper describes the first application of this assay to plant cells for genotoxicological assessment. Germinating Vicia faba (field bean) seedlings were kept in water with either methyl methanesulfonate (MMS), ethyl methanesulfonate (EMS), mitomycin C (MMC), cycloheximide (CH), cadmium chloride (CdCl2), potassium dichromate (K2Cr2O7), or chromium trichloride (CrCl3). Nuclei were isolated from the root cells and evaluated for the extent of DNA migration. With the exception of cycloheximide, all agents induced a significant increase in DNA migration. These results indicate that the comet assay may be a valuable tool for monitoring DNA damage in plant systems. However, there was a significant heterogeneity in the extent of DNA migration within and between seedlings, which may be intrinsic to the assay or indicative of sampling problems.