A total of 319 heterotrophic bacteria were isolated from seawater samples of Tokyo, Sagami and Suruga Bays, and the north Pacific Ocean, and their phosphatase production was tested. The ratio of phosphatase producers increased with the distance from the coast; that is, the proportions were 11% in Tokyo Bay, 48% and 55% in Sagami and Suruga Bays, respectively, and 63% in the Pacific Ocean. The constitutive phosphatase producers accounted for 75% of phosphatase-producing bacteria in oceanic regions, whereas they accounted for only 25% in coastal regions. The dominant genera of phosphatase producers in each region were Vibrio in Tokyo Bay, Vibrio and Pseudomonas is Sagami and Suruga Bays, and Pseudomonas in the Pacific Ocean. The proportion of phosphatase producers in the Pseudomonas group increased with distance from the coast.