Agricultural soil carbon (C) sequestration through conservation management is a viable option to improve environmental quality. To evaluate the impacts of no-till (NT) on C sequestration in soil, composite soil samples at 0-7.5, 7.5-15, 15-22.5 and 22.5-30 cm depth were randomly collected from 2, 8, and 40 yr NT, and conventionally tilled (CT) plots in NW Agricultural Research Center at Wood County, northern Ohio in fall of 2004. Soil samples were processed and analyzed for total (T_OC), particulate (P_OC), active (A_C), passive (P_C), extractable (Ext C), and soluble C (Sol C) with selected basic properties. The concentration and mass of T_OC, P_OC, A_C, P_C, and Ext C increased in NT soils compared to CT soils. Temporal effects of NT were more pronounced on A_C and P_OC than on T_OC, Ext C, and Sol C at different soil depths. On average, tillage effects were more pronounced at surface than at subsurface soil depth. Combined over soil depths (0 to 30 cm), the storage of T_OC, P_OC, A_C, and P_C pools varied significantly in response to NT. When plotted the difference of NT-CT mass of T_OC, P_OC, A_C, and P_C with time, a significant quadratic increase in C sequestration was observed in response to long-term NT. Results suggested that C sequestration in soils under long-term NT compared to CT is possibly due to surface deposition of crop residues, less disturbance, slow and efficient decomposition of residues, and greater physical protection.