Parasitological examination was conducted in 10 cases of sudden death which occurred in calves raised in the southern part of Japan where sawdust litter confinement pens were used. Extensive infection of the small intestine with Strongyloides papillosus (SPL) was observed in every necropsied case. Inspection of the pens where the fatal cases were detected revealed the presence of a number of infective larvae of SPL in sawdust litter, suggesting that this material was conducive to the growth of the larvae and that per cutem infection of calves with the larvae was promoted by the use of this management system. The scabs, which were occasionally found at coronary bands in the field cases, were considered to result from per cutem infection with the larvae. The autopsy revealed the presence of some migratory larvae in various tissues. An attempt was made to reproduce the sudden death symptoms by experimentally infecting calves with the larvae. Ten calves which were infected per cutem with more than 320,000 larvae per 100 kg of body weight died suddenly from 10.8 to 27.4 days after the infection. Clinical and parasitological findings in these experimental cases were similar to those of the field cases. Outbreaks of the disease in the farms ceased following the administration of thiabendazole or ivermectin.