Field studies were performed in the years 1986-1990 on the incidence, severity and harmfulness of eyespot (Pseudocercosporella herpotrichoides) on naturally infected winter wheat cultivated in 6 regions of Poland. In average, over one-third of plants showed infection symptoms at GS 75-85 (ripening), the severity of the disease being predominantly low. On the basis of data recorded, infection indices (Scott and Hollins 1978) and percentages of grain yield losses (Clarkson 1981) were calculated for each year and region. Data are also given on the influence of disease on selected yield components, and on the effect of lodging on the occurrence and severity of eyespot, as related to grain yield, and some aspects of its quality. Average grain yield losses accounted for 2.37%, being the highest in south-eastern region (3.55%) and south-western region (3.52%), and the lowest in north-eastern (1.32%) and central (1.58%) regions of winter wheat cultivation in Poland.