A system has been developed for rapid selection of streptomycin resistant mutants, as adventitious shoots arising from explants of several Solanaceous species. Efficient mutagenesis was achieved by incubating shoot culturederived leaf strips with 1 or 5 mM nitroso-methylurea, for 90 or 120 min. In Nicotiana tabacum and Lycopersicon peruvianum these treatments resulted in white or variegated adventitious shoots from up to 3.5% of explants placed on medium promoting shoot regeneration. Chlorophyll deficiencies were only observed very rarely in Solanum nigrum. Streptomycin resistant shoots were obtained from leaf explants placed on medium containing 500 mg 1- 1 streptomycin sulphate, under which conditions ex plants are bleached and adventitious shoot development suppressed. Green adventitious shoots appeared at a frequency dependent both on the mutagenic treatment and on the species. The best response was with S. nigrwn where > 70% of the ex plants produced streptomycin resistant shoots, most of which retained their resistance on subsequent testing. Maternal inheritance of streptomycin resistance has been confirmed for several N. tabacum and S. nigrum mutants, and there is also evidence for paternal transmission in the latter species. The procedure h3.s been successfully extended to other species, including N. s_vlvestris and N. plumbagin (fOlia, and also to obtain spectinomycin resistant mutants.