The potent food mutagen and carcinogen 2-amino-3-methyl-imidazo[4, 5-f]quinoline (IQ) and the structurally related heterocyclic aromatic amines 2-aminoimidazo[4, 5-f]quinoline (demethyl-IQ) and 2-amino-l-methylinudazo(4, 5-f)quinoline (iso-IQ) were assayed for genotoxicity in the wing somatic mutation and recombination test (SMART) as well as in the sex-linked recessive lethal (SLRL) test in Drosophila melanogaster. In addition, 3-methyl-2-nitroimidazo[4, 5-f]-quinoline (nitro-IQ), 2-nitrofluorene and 1, 8-dinitropyrene were also assayed in the wing spot test. IQ was clearly muta-genic in the SLRL test with highest activity in spermatids. Iso-IQ was more active than IQ whereas demethyl-IQ was inactive in this test. The same pattern of results was obtained in the wing SMART: iso-IQ produced >2-fold higher frequencies of spots than IQ and demethyl-IQ was clearly negative. In addition, nitro-IQ exhibited an approximately equal genotoxic activity as IQ. 2-Nitrofluorene and 1, 8-di-nitropyrene were both inactive in the wing spot test. These data provide good evidence for a correlation of genotoxic effects in germinal and somatic cells, and for the practical advantage of the wing spot test in Drosophila. Moreover, the results show structure-activity relationships among the heterocyclic aromatic amines and nitro compounds similar to those found in Salmonell