Field studies were carried out at the experimental farm, Faculty of Agriculture, Kafr El-Sheikh University during two successive seasons, 2004 and 2005 to study the seasonal abundance of soybean stem fly, Melanagromyza sojae (Zehntner) and leafminer, Liriomyza trifolii (Burgess) on three soybean cultivars, the relative susceptibility of soybean cultivars to infestation and the relationship between both soybean plant height and number of plant trifoliate leaves and infestation with M. sojae and L. trifolii under field condition.  Results showed that M. sojae generally infested three soybean cultivars (Giza 35, Giza 82 and Clark) throughout tow seasons. Also, M. sojae had three peaks for mines, larvae and pupae during both seasons. Population density of M. sojae mines, larvae and pupae in 2005 season was higher 2004 season on three soybean cultivars. Statistical analysis showed highly significant differences among soybean cultivars to infestation with M. sojae during 2004 and 2005 seasons. Giza 35 variety was the most resistant variety to infestation with M. sojae in the first and second seasons. Positive significant correlation was recorded between soybean plant height and infestation with M. sojae in both seasons, while this correlation was positive between number of soybean trifoliate leaves and M. sojae infestation. M. sojae larvae showed negative correlation in two cases. Concerning leafminer, L. trifolii results showed that this insect had two peaks on the three soybean cultivars, in August and September in both seasons. Population density of L. trifolii in 2005 season was higher than 2004 season. Statistical analysis showed highly significant differences among three cultivars to infestation with L. trifolii in both seasons. Giza 82 was the most resistance variety to infestation. Significant positive correlation was recorded between L. trifolii infestation in first season and both soybean plant height and number of plant trifoliate leaves. Also, significant correlation was found for Giza 82 in the second season in two cases. It could be concluded that, Giza 35 cultivar was the most suitable one cultivated, because it is resistant to M. sojae and moderately infested by L. trifolii.