Studies were conducted to characterize the diversity of degradative abilities of microbial communities from pristine aquifer solids samples. Biodegradation was measured in aquifer solids slurries as both the conversion of radiolabeled substrate to (14)CO2 and the incorporation of label into cell biomass. The microbial community degraded aniline hydrochloride, chlorobenzene, p-chlorophenol, m-cresol, ethylene dibromide, naphthalene, phenol, toluene, and trichlorobenzene. Several kinetic parameters were calculated from the uptake and mineralization data. The results show that uptake into cell biomass represents a large fraction of total metabolism for many of the xenobiotic compounds. (Copyright (c) SETAC 1988.)