#The Purpose of this study was to identify the underlying causes of rural-urban migration in Iran for the period 1966-76. Twelve hypotheses were investigated to ascertain the effect of the structure of agriculture population pressure on land, incom, education, urban-rural a menity differentials and road availability in rural areas on rural out-migration. Based on published data hypotheses werw tested by the utilization of correlation coefficients and regression analyses. It was found that existence of rain fed landholding in sizes of 50 hectares or more had an inverse relationship with rural out migration. The propprtion of the population empoloyed in agriculture, the population pressur on irrigated agricultural lands and rural income had significant negative relationship whit rural migration