Albino mice (Balb c/nut) experimentally infected with Heligmosomoides polygyrus were treated with levamisole hydrochloride ('Nemicide'--ICI Pharmaceutical PLC) by oral drenching or subcutaneous injection at 5, 10 and 20 mg kg-1. Faecal egg counts monitored for two or three days after dosing and post-mortem worm counts were used to assess the efficacy of these treatments. The lowest dose rate gave poor clearance of adult worms but at 10 and 20 mg kg-1, 91 and 96% reductions in worm burden were achieved. Reduction in post-dosing faecal egg counts were variable. Neither method of administration offered particular advantage in terms of efficacy. Faecal egg count data gave inconsistent differences and at necropsy, worm counts were lower in mice dosed orally but not significantly so.