Two sets of trials were conducted during the 1994 and 1995 dry seasons at Samaru in the Northern Guinea Savanna agro-ecological zone of Nigeria to study the effect of period of weed interference and chemical weed control on the growth and yield of garlic (Allium sativum L.). In the weed interference trials, weed infestation initially for 3 WAP did not cause any significant depression in the growth and yield of garlic as reflected in crop viguor score, plant height and number of fully opened leaves per plant and bulb yield. Subsequent weed removal after initial infestation for 9 WAP did not ameliorate the depression in the growth and yield of garlic caused by weed interference compared with weed infestation until harvest. Uncontrolled weeds throughout the crop life cycle caused 70% and 80% reduction in garlic yield in 1994 and 1995, respectively, compared with the maximum obtained with the crop kept weed-free throughout. The critical period of weed competition was observed to be between 5 and 6 WAP in both years. In the weed control study, all the herbicide treatments effectively reduced weed infestation compared with the hand weeded control. In the two years, oxadiazon applied alone at lOOOg a.i/ha and 1500g a.i./ha, the mixture with chloroxuron at 750+1000g a.i./ha and 750+2000g a.i./ha and with prometryne at 750 +1000g a.i./ha and 750+l500g a.i./ha resulted in high garlic bulb yield that were comparable to that of the hoe-weeded control. The treatment effectively controlled weeds without phytotoxicity on the crop.