The inactivation rates of digester-resistant parasite eggs in laboratory-stored sludge were measured to determine their potential fate in sludge lagoons. Eggs from roundworms (Ascaris, Toxocara and Trichuris) and a tapeworm (Hymenolepis) were added to domestic sludges either before and during, or after aerobic or anaerobic digestion. Digested sludge samples seeded with the parasite eggs were stored in the laboratory at 4 C, 25 C, and in a container that was inserted in the ground to simulate sludge storage conditions. Non-sludge soil samples (controls) were seeded with the same parasites as the digested sludges and stored under similar conditions. Though storage temperature and storage time were the most important factors in the inactivation of these eggs, minor effects were also associated with other factors--type of sludge digestion, timing of egg addition, type of storage (in sludges versus soil), pH, and species of egg. These controlled laboratory studies suggest that sludge lagooning can be an effective method for eliminating parasite eggs, particularly in warmer geographic locations.