The paper describes the influence of birth and migration rates of peasant population on their farm proportions. The author ascertained that the agricultural areas in Poland became filled with population about two hundred years ago and afterwards overpopulation grew there. The reasons for this were the high birth rates of the peasant population. Only in 1945 was that course inverted. Though since then the peasant migration has considerably increased still its birth rates remained high and, as a result the decrease of peasant population till 1990 was insufficient and the agricultural structure remained defective. The situation of Polish agriculture in the integration process with the EU will be difficult.