Field trials were carried out over a three year period in an alfisol in a subhumid tropical environment to evaluate the effectiveness of hand-weeding frequencies and several herbicides for weed control in cassava (Manihot esculentaCrantz). Uncontrolled weed growth caused 40% reduction in root yield of short, profusely branching cassava cultivar while a 68% reduction in root yield was observed in separate studies involving a tall non-branching cultivar. Two or three properly timed hoe weedings gave crop yields that were as good as keeping the plots weed free throughout the growing season. Although pre-emergence application of fluometuron at 2.0 to 3.0 kg a.i./ha or diuron at 2.0 kg a.i./ha used singly gave good weed control and crop yield, the efficacy of these herbicides was greatly improved by tank mixing each of them with alachlor or metolachlor at 3.0 and 2.0 kg a.i./ha respectively. Excellent crop yield was also observed where atrazine and metolachlor was applied pre-emergence at 2.5 kg a.i./ha. At current labour rates in Nigeria, it is cheaper to practise chemical weed control in cassava than to rely on hand-weeding even if the labour is readily available and the weeding can be carried out on time.