Aggregation and soil organic carbon(SOC)concentration representintegrated effects of soil type,environment,plant species,and soil management practices.This study was conducted to assess effect of water regime on size distribution of soil aggregates and C concentrations therein in paddy soils developed under different water conhditions from purple soils in a purple hilly area of the Sichuan basin.The labile organic carbon,microorganism biomass carbon,water dissolved carbon,and organic carbon concen trationin aggregates of different sizes gained by the wetting sieve method were deter mined.The content of aggregates >2 mm in diameter was the highestin the cultivated horizon of gleyed paddy soils and percogenic paddy soils,being 76.65% and 75.92%,respectively,and only 13.10% in the cultivated horizon of sub-mergeric paddy soil.