Field experiments were conducted during the 1995 and 1996 wet seasons at the Research Farm of the Institute for Agricultural Research, Samaru, Zaria (11° 11 N; 7° 38 m; 680m above sea level) in the northern Guinea Savanna zone of Nigeria. The study was conducted to evaluate the effects of inter-row spacing (seed broadcast, 30, 60 and 90cm) on the efficiency of four preemergence herbicides (imazaquin, metolachlor + metobromuron, metolachlor •+- diuron and simazine + ametryn) each applied at two rates on sesame. The different herbicide treatments gave varying significant effects on the performance of the crop. While metolachlor + metobromuron at 0.75 + 0.75 and 1.0 + 1.0kg a.i./ha, imazaquin at 0.20kg a.i./ha and metolachlor + diuron at 1.0 + 0.25kg a.i./ha provided good weed control and were well tolerated by the crop, the application of metolachlor + diuron at 1.0 + 0.5 and 1.5 + 0.5kg a.i./ha and also simazine + ametryn at 0.75 + 0.75 and 1.0 + 1.0kg a.i./ha were phytotoxic to the crop resulting in significant stand and yield losses. Inter-row spacing also had significant effect on the yield and related parameters of sesame. The highest values for number of branches, capsules, dry matter production, seed yield per plant and seed weight were obtained under the inter-row spacing of 90cm, while the maximum values for plant height and number of stands were obtained under seed broadcast. However, the maximum seed yield of 401.00 and 511.26kg/ha were obtained from the application of metolachlor + metobromuron at 1.0 + 1.0kg a.i./ha under 30cm inter-row spacing in 1995 and 1996, respectively. Yield reductions of 81 and 88% were recorded in 1995 and 1996 cropping seasons, respectively, due to unrestricted weed growth throughout the crop life cycle