The infection with tapeworm of the Mesocestodes sp. has been rarely reported and only 8 cases of human infection were found in the world up to date. This is to report the first case of human infection with this tapeworm belonged to Cyclophyllidea in Korea. In January 1967, a 45 years old man visited to the out clinic of St. Mary's Hospital with the complaints of intermittent indigestion and abdominal distension nearly for 1 year. Laboratory findings appeared almost normal except increased eosinophils up to 14 per cent. The characteristic ova of Mesocestoides sp. were found by the serial stool examinations, which contained hexacanth larva inside the egg shell without operculum as in Cyclophyllidea. It was failed to reveal the scolex by the first evacuation, but one among 3 worms evacuated by the treatment with atabrine and enough purgations 2 months later, has been found the characteristic scolex. They were 85 cm to 136 cm long and the scolex had 4 distinct suckers but no rostellum, the matured proglottid had numerous testes bilaterally and ovary with yolk glands in central parts, and in the gravid proglottid spiral uterus was opened to uterine pore and characterized by the spherically distended uterine capsules. The patient had the history of ingestion of 15 snakes as raw about 1 year ago as usually seen in Japanese cases.
