Monoculture and intercropping systems for yam (Dioscorea rotundata Poir) and sweet potato (Ipomoea batatas) production in two planting seasons were evaluated at the Corozal Agricultural Experiment Substation. In Experiment 1, yam cv. Guinea Blanco and sweet potato cv. Dominicana were planted the same date; and sweet potato 6 weeks before or after yam in February, April and May. In Experiment 2, the same cropping treatments were evaluated, but plantings were made in October and December 1983 and in January 1984. In this experiment Guinea Negro yam was used. In Experiment 1, sweet potato planted in monoculture or intercropped suppressed weed growth. However, the yam competition significantly reduced sweet potato yields. Although weeds grew freely in monoculture planting, yields were not significantly reduced. In Experiment 2, no significant differences were detected among cropping systems with regard to weed control. However, late plantings (December and January) reduced the weed population in both planting systems. When yam and sweet potato were intercropped during these months, the association did not affect yam production but did reduce sweet potato yields. The yam-sweet potato intercropping planting of December yielded highest for yams with 36,738 k/ha, and the highest combined yam-sweet potato tuber production with 59,014 k/ha. The sweet potato planted as a monoculture in December yielded (36,559 k/ha).