The removal of intestinal nematode eggs in waste stabilization ponds treating domestic waste-water was studied in northeast Brazil. Anaerobic and primary faculttive ponds achieved Ascaris spp. removals of 88-98% and 99-100%, and hookworm removals of 91-97% and 98-100%, respectively. Egg-free effluents were produced by a single primary facultative pond with a retention time of 18.9 days, and by an anaerobic and a secondary facultative pond in series with retention times of 6.8 and 5.5 days. It is concluded that effluents with .ltoreq. 1 egg per liter can be produced by a 1 day anerobic pond followed by a 5 day secondary facultative and a 5 day maturation pond.