A single sample of hydrocarbon-contaminated soil was enriched under aerobic conditions in a mineral medium supplemented with tert-butanol (1 g/L) as sole carbon source, or with methylamine (2 g/L) as main carbon source and tert-butanol (0.1 g/L) as cosubstrate. The mixed cultures obtained after four serial transfers were used for further experiments. In a growth experiment, the concentration of tert-butanol declined slowly after an initial lag phase. Cell suspensions of the mixed culture or of methylamine-grown cells incubated with tert-butyl methyl ether showed no similar decline in substrate concentration during 6 weeks. The results suggested the possible persistence of tert-butyl methyl ether, and that the tertiary butyl group is not itself the determinant of resistance to aerobic biodegradation