In the years 1999-2001 in the Garlica Murowana Experimental Station the thinning of fruit sets on Sampion apple trees was carried out manually or chemically with urea. The effects of the treatments on fruit setting, total yield, and the weight and diameter of fruit were investigated. Manual thinning of fruit sets effected a decrease in the number and an increase in the weight of apples. Urea applied at the end of blooming strongly thinned the fruit sets yet it favourably affected the weight of apples. The results of the experiment show that spraying trees with urea by the end of April and a week after blooming favourably affects the yield of' fruit.