This investigation was carried out during 1988/1989 and 1989/ 1990 seasons to study the effect of intercropping onion plants (cultivar Giza 20) with cotton (cultivar Giza 76). The study involved 9 treatments (3 patterns x 3 plant spacings) of relay cropping of onion and cotton. The agronomic traits, yield, competition ability and land equivalent ratio were studied. Solid onion and those transplanted at 5 cm outyielded all treat-ments in the second season only. Average bulb weight was increased with solid onion and when inter-cropped on ridges 60 or 90 cm width, besides, transplanting on 10cm distance in both seasons. Combinations of P1xa, P2xa and P3 x a as well as solid one (280 000 plants/fed.) gave the highest onion yield/fed. Highest bulb weight was obtained by the combination of P1xc, P2xc and P3 x c (140 000 plants/fed.). Germination %, plant height, No. of fruiting branches, earliness, seed cotton yield/fed average boll weight and No. of unopen bolls per plant were not significantly affected by intercropping patterns or trans‌planting spacings of onion, in both seasons. Solid cotton planting as well as those intercropped on ridges 60cm were surpassed significantly in number of open bolls/plant in both seasons too. Onion was the dominating crop. Competition ability of both crops was increased as the ridge width increased from 60 up to 120 cm. Cotton gave the positive value of agressivity which decreased as the distance between onion plants increased from 5 up to 10 cm (i.e. 280 000 and 140 000 plants/fed., respectively). Cotton was the domi‌nant crop under all onion plant spacings. The highest Land equivalent ra‌tio was achieved by planting 280, 000 plants of onion/fed.