Decades of surveying helminthic diseases in domestic and free-living ruminants in the CSR evidenced extensive infestation by lungworms, gastrointestinal nematodes, and liver flukes. In some years, parasitic invasion caused up to 50% of total losses of roe deer. Programmes to control systematically dictyocaulosis and fascioliasis were carried out with cattle and sheep in 1970-1980, with deer in 1981-1985. In the eighties, the incidence of F. hepatica in cattle and sheep dropped to less than 1%, of D. viviparus in cattle to 0.2%; no D. filaria is to be encountered in sheep presently. The share of parasitic diseases in total losses of roe deer decreased to 19% in 1983-1985.