Abstract: The population densities of the bacterial microflora in the soil and rice seed, samples collected from the cultivated (plowed) and uncultivated (unplowed) rice fields previously planted with hairy vetch, Chinese milk vetch (Cmv.) and clover were assessed during 1997 and 1998. The antagonistic effects of the bacterial isolates against different rice pathogens were also studied in vitro. The population density in soil of the cultivated field differed considerably from uncultivated one. The THB (Total Heterotrophic Bacteria) and Bacillus populations were higher in the cultivated field than the uncultivated one regardless of the crop planted previously. The THB population was lower in 1997 than in 1998. The trend was reverse for Bacillus. Pseudomonas had a high population in the uncultivated field in 1997 while it was high in the cultivated field during 1998. Rice seeds collected from cultivated fields harbored a high population of THB, Pseudomonas and Bacillus. However, bacterial populations were higher in 1997 than in 1998. In the soil, Bacillus was higher than Pseudomonas but the trend was reverse in the seed. Out of the 630 and 82 isolates from soil and seed samples, 130 and 45 isolates showed antagonistic activity against different rice pathogens in vitro, respectively.