The bacteriological impact of fish waste dumping in the ocean was evaluated by comparing heterotrophic bacterial counts for seawater and sediment at the dump site with those from a control site. Prior to dumping, fish waste contained 3.0 x 10(7) bacteria g-1. Seawater near the ocean floor (bottom water) and sediment from the dump site contained 4.1 x 10(2) bacteria ml-1 and 2.2 x 10(6) bacteria g-1, respectively. Bottom water and sediment samples from the control site contained significantly lower bacterial counts (< 10(2) bacteria g-1 and 6.1 x 10(4) bacteria g-1, respectively) than the dump site samples. For the five aerobic media tested, significant differences in bacterial counts occurred only for the fish waste samples. Anaerobic bacterial counts, for all samples except fish waste, were slightly less than the aerobic bacterial counts.