Sphingomonas species were commonly isolated from biofilms in drinking water distribution systems in Finland (three water meters) and Sweden (five water taps in different buildings). The Sphingomonas isolates (n = 38) were characterized by chemotaxonomic, physiological and phylogenetic methods. Fifteen isolates were designated to species Sphingomonas aromaticivorans, seven isolates to S. subterranea, two isolates to S. xenophaga and one isolate to S. stygia. Thirteen isolates represented one or more new species of Sphingomonas. Thirty-three isolates out of 38 grew at 5 degreesC on trypticase soy broth agar (TSBA) and may therefore proliferate in the Nordic drinking water pipeline where the temperature typically ranges from 2 to 12 degreesC. Thirty-three isolates out of 38 grew at 37 degreesC on TSBA and 15 isolates also grew on blood agar at 37 degreesC. Considering the potentially pathogenic features of sphingomonas, their presence in drinking water distribution systems may not be desirable.