A study was made on intercropping of mungbean and peanut with field corn. Two varieties of mungbean, PSU 1 (VC 2768A) and KPS 2 (VC 2778A) and a peanut variety, Tainan 9, were planted within-row or intra-row of corn variety, Suwan 1, using a split-plot design. Different spacings of corn namely 70 x 30 cm 1 plant/hill with one hill of legume, 70 x 60 cm 2 plants/hill with one hill of legume, 70 x 60 cm 2 plants/hill with two hills of legume, 70 x 90 cm 3 plants/hill with two hills of legume and 70 x 90 cm with three hills of legume. The results showed that sole cropping of corn gave average yield over all spacings of 735.27 kg/rai. The spacing of 70 x 30 cm with one plant/hill gave the highest yield of 825.04 kg/rai. The average yield of corn obtained from all intercropping treatments was 694.30 kg/rai. The most suitable spacing for intra-row corn and legume cropping was 70 x 60 cm 2 plants/hill with 2 hills of legume. The average yield of this treatment over all legumes was 947.89 kg/rai. The sole cropping of mungbean yielded 324.33 kg/rai, Whereas that of intra-row cropping was only 66.93 kg/rai. The reduction of seed yield was due primarily to the tlow number of mungbean plants per unit area and to the reduction of certain yield components, particularly weitht of seed-plant which reduced from 10.14 g in sold cropping to 5.41 g in intra-row cropping and number of pods/plant decreased from 19 to 11 pods. However, no obvious changes were observed for seed size and pod length. Sole peanut yielded 214.30 kg/rai, whereas that of intra-row cropping yielded 25.03 to 60.87 kg/rai. The reduction of yield was also due to low population density and the reductiion of seed weight per plant from 6.70 to 3.28-4.47 g. The effect of shading from all intercropping treatments varied due to spacings. The 70 x 30 cm spacing of corn with 1 plant/hill produced more shade than all other spacing at 20 to 60 days after planting. However, at 80 to 100 days after planting the corn spacing of 70 x 90 cm with 3 plants/hill produced more shade than others. Returns due to intercropping wer evaluated by using the land equivalent ratio (LER). It was found that the corn spacing of 70 x 60 cm. 2 plants/hill with two hills of legume gave a high LER of 1.52 of which the highest LER was 1.62 obtained from corn-peanut intercropping. In conclusion, when suitable spacings was used, intercropped legume may promote the yield of corn.