Field experiments were conducted to study the effect on weeds and crop yield under maize + blackgram intercropping system at Raipur during 2004 and 2005. Treatments consisted of five planting geometry viz., sole maize, sole blackgram, maize +blackgram (1:1), maize + blackgram (2:1) and maize + blackgram (2:2) and four weed management practices viz., weedy check, hand weeding (HW)  at 30 DAS, alachlor  2.0 kg/ha as pre-emergence and alachlor  1.5 kg/ha as pre-emergence + HW at 40 DAS. Grain yield, productivity rating index (PRI), production efficiency (PE) and weed-control efficiency (WCE) were the highest under maize + blackgram (2:1) for maize. However, weed smothering efficiency of maize was highest under maize + blackgram (1:1). At harvest of blackgram (75 DAS) and maize (105 DAS), the dry weight of weeds were the lowest with alachlor  1.5 kg/ha + HW at 40 DAS. This treatment produced maximum grain yield, PRI and PE of maize and blackgram.