Population sizes of three bacterial species were examined in stream benthic habitats to assess differences in distribution and culturability among species. Population sizes were determined in sediments (both near bank and mid-channel) from three sites along Four Mile Creek (South Carolina, USA) using both culture-dependent (colony hybridization) and culture-independent (fluorescent in situ hybridization) techniques. The two methods used yielded different results. The numbers of colony forming units (CFU) of each species were similar in pattern to that found when the total number of CFU was enumerated (i.e., greater abundance in bank sediments and at downstream sites). In situ hybridization revealed a different distribution of these bacterial populations. Population sizes of the species were similar among sites. By using both the culture-based method and the culture-independent methods, the culturability of each species could be determined. The culturability of each species was at times much higher than the culturability of the overall assemblage. In spite of this higher culturability, viable but non-culturable cells commonly dominated the populations examined. These findings suggest that not only do bacterial species differ in population size and distribution, but also that cells within a population differ in their physiological state, or response to their environment, as reflected in differences in culturability.