The effect of major production factors (forecrop, fertilisation, irrigation, soil cultivation and soil preparation) on the yield components and yield of winter wheat were studied in a long-term experiment set up at the Látókép Experimental Nursery of the Agricultural Sciences Centre of the University of Debrecen. The results of regression analysis led to the following conclusions: • In our experiments in 2000, after using maize as a forecrop –based on the results of analysis of regression – fertilisation determined the yield. • After using pea as a forecrop, a N50 P35 K40 kg/ha fertiliser rate led to an economical increase in the yield of winter wheat. • None of the determinative yield components varied significantly for winter wheat produced after using pea as a forecrop. • There is a closed, significant correlation between plant height, spike length, plant and spike mass, the number of spikelets and grains per spike after using maize as forecrop. The thousand grain mass is different from the other yield components, because it is not part of the relation system of those yield components. • The increased yield of winter wheat after maize has been used as a forecrop is due to the positive change in grain number per spike yield component.