Macrobenthic animal communities that colonized uncontaminated and creosote-contaminated sand during 8 weeks were compared to assess effects of marine-grade creosote on community structure. Aquaria were colonized in the laboratory by planktonic larvae entrained in continuously supplied unfiltered seawater and in the field by animals that occurred naturally. Individuals and species in aquaria that contained 844 and 4420 micrograms creosote/g were significantly fewer than those in the control. Abundance of animals in field-colonized communities contaminated with 177 micrograms/g, but not in laboratory-colonized communities, also was less than that in the control. The lowest concentration at either site that affected numbers of individuals or species was 844 micrograms/g for mollusks and 177 micrograms/g for echinoderms, annelids, and arthropods. Initial measured concentrations of creosote in sand (mid-range concentration) decreased by 30% in the laboratory and by 42% in the field at the end of the eight-week test.