The autoinfective filariform larva of Strongyloides stercoralis causes hyperinfection in immunosuppressed hosts. Here we report on the case of a male patient who was admitted to the emergency room at Gwangju Veterans Hospital with a complaint of dyspnea, and who was receiving corticosteroid therapy for asthma. Many slender larvae of S. stercoralis with a notched tail were detected in Papanicolaou stained sputum. They measured $269pm21.2{mu}m$ in length and $11pm0.6{mu}m$ in width. The esophagus extended nearly half of the body length. The larvae were identified putatively as autoinfective third-stage filariform larvae, and their presence was fatal. The autoinfective filariform larva of S. stercoralis has not been previously reported in Korea.