The performance of a laboratory-scale Sequencing Batch Reactor (SBR) has been studied in aerobic-anoxic sequence for simultaneous organic carbon and nitrogen removal. The reactor was operated under three different variations of aerobic-anoxic sequence, viz. 4+4, 5+3 and 3+5 hours with input solutions of soluble COD (SCOD) level 1000 +/- 100 mg/L and initial ammonia nitrogen of 40 and 90 mg/L. It has been observed that 85 to 92% of SCOD removal would be possible at the end of 8.0 hour of overall reaction period, irrespective of the length of the aerobic react period. In the case of 4+4 hour operating cycle, reasonable degree of nitrification (88-100%) and denitrification (73-75%), along with 91-94% of organic carbon removal have been achieved, which has been considered to be the optimum performance of the reactor.