Aeromonas spp. are widely distributed in the aquatic environment. In Bangladesh, seasonal distribution of these organisms in aquatic environment was studied during July 1986-August 1987. Water, sediment, plant, and plankton samples were collected monthly from the Dhanmondi lake and the Buriganga river during the study period. Aeromonas spp. were isolated from all samples throughout the year. The seasonal peak of Aeromonas spp. was observed in warmer months (April-May) in the surface waters. In the sediment, the highest peak was observed in March and August. In most plants, the highest peak was observed during the winter months (December-February). In the plankton samples of the Dhanmondi lake and the Buriganga river, the highest counts were obtained in July and February respectively. In both the sampling sites, plants were observed to contain more Aeromonas than did the water and sediment samples. The prevalence of Aeromonas spp. throughout the year in aquatic environment suggests the autochthonous nature of these organisms and that there is an association of Aeromonas with the aquatic environment.