Two cowpea varieties, VITA #5 &Jungweon local var., had been sown at intervals of 15 days from May 1 to Aug. 29, and the following results were obtained. The earlier the two varieties had been sown, the shorter period from planting to first blooming and maturing, the more peduncles, the more pods per peduncle and plant, the heavier 100-grain weight, and the more grain yield we had. VITA #5 was earlier in maturity and higher in yielding performance than Jungweon local var., and both could not bloom in late sowing after Aug. 14. During the period of flowering and seed-setting, bad weather condition decreased the number of grains per pod. Limit sowing date of VITA #5 was Jun. 30 and that of Jungweon local var. was Jun. 15 in the middle part of Korea. Growing degree days (GDD) was available in cowpea.