For estimation of mung bean row orientation and planting date, a field study was conducted in Research Field of Islamic Azad University, Shahr-e-Rey Branch, Tehran, Iran in 2007. The experiment was planted as a randomized complete block design with split-plot arrangement and four replications in which treatments consisted of two seeding methods: seeding with east–west and north–south row orientations. Planting date of main plots is 5th and 20th of May and 6th of June for subplots. The results of analysis of variance for row orientation showed significant effects on grain yield, biomass, leaf wet weight, harvest index and fruit wet weight. Grain yield in east- west row orientation was 455 g/m2 while this factor in another orientation method was 379 g/m2 and it represented more than 16% yield loss on this condition. Effect of planting date on many of traits had significant effects which include grain yield, biomass, harvest index, and the number of seed per pod. The first planting date (5th May) with 479 g/m2 had the highest grain yield.
