N-(4-[(1-(Dimethylamino)-ethylidene)-amino]-phenyl)-2 methoxyacetamide hydrochloride (amidantel, BAY d 8815) is an aminophenylamidine with an interesting anthelminthic spectrum. In rodents the compound is active against nematodes, filariae and cestodes. Of special interest is the high efficacy in dogs against hookworms and large roundworms. Amidantel was well tolerated by all animals tested and did not show teratogenic effects. The drug was moderately potent inhibitor of both E. electricus and C. elegans acetylcholinesterase but at concentrations too high to account for its abilitiy to contract cut worms. The primary mode of action of amidantel appears to be as agonist at the level of the acetylcholine receptor, a view supported by the observation that its effect may be blocked by the nicotinic antagonists d-tubocurarine and gallamine. Amidantel was also investigated it clinical trials as the treatment against Ancylostoma duodenale infection. Amidantel proved to be very effective against A. duodenale as well as Ascaris lumbricoides. With regard to dosage, a single dose of 6.0 mg/kg body weight of amidantel was found to be the most effective and well tolerated than the other dosages employed.