The mutagenic effects of several inhaled anesthetic agents were investigated using the sex-linked recessive lethal assay in the fruit fly,Drosophila melanogaster. Male wild-type flies were exposed for 1 hr to either halothane, enflurane, isoflurane, or fluroxene at vapor concentrations of 1 or 2% or to nitrous oxide at concentrations of 40 or 80%. Control flies were exposed to air alone. Following treatment, male flies were mated with untreated virgin females of theBascstrain and the rate of sex-linked recessive lethals was determined in the F2generation. Halothane and fluroxene produced a dose-dependent and statistically significant increase in the rate of sex-linked recessive lethals, whereas enflurane, isoflurane, and nitrous oxide were not mutagenic at the concentrations tested.