Abstract Field experiments were conducted in 1993 and 1995 in Cameroon to determine the critical period of weed control in common bean ( Phaseolus vulgaris L.), and the effect of location and cultivar. Bean yield loss increased with increasing duration of weed interference, and decreased with increasing duration of weed control. The critical period occurred between emergence and second trifoliate leaf for cultivar Maringue, respectively at Dschang (1993) and Yaoundé (1995), and between first trifoliate leaf and pod filling stages of bean growth for other trials. Generally, the critical period was less than 25 days at 5% yield loss level, and non-existent in 50% of the trials when 10% yield loss was considered. The short critical period observed suggests that in Cameroon, irrespective of location and cultivar, a single weed removal well timed is sufficient to prevent yield loss in bean.