Five cases infected with Rhabditis sp. were detected in a survey to examine the stool specimen from rural primary school children. A large number of the larvae of Rhabditis sp. detected by the direct cellophane thick smear were cultured by the filter paper method. The examination was carried out in April through June 1980 in Tangjeong-Myon, Ahsan-Gun, and in September 1983 in Sandong-Eup, Yeongwol-Gun. The results obtained in this study were as follows: Prevalence: Out of 925 children, 5(0.54 percent) children were found to be positive. The number of the detected larvae was 110/0.1 gm of feces in case 1, 35 in case 2, 130 in case 3, 86 in case 4 and 62 in case 5. Larvae: The larvae were prepared by means of the direct fecal smear and measured by a µm equipped in the microscope. Twelve(12) through 15-day old larvae in culture were 197.1 µm long in average, and the maximum size of the matured stage larvae was 884.0 × 25.9 µm. However, the length variation was ranged as 173.0 to 884.0 µm. Adults: The size of clubbed adult female was 1,357 µm(1,176-1,419) in length and 80 µm(79-82) in width. Length of buccal cavity was 33 µm. A long cylindrical esophagus (273 µm) of the worms with a valved posterior cardiac bulb and with median bulbar swelling was morphologically indicated. Distance from mouth to vulva was occupied 58 percent of body length. Male worm was 1,006 µm (890-1,148) in length and 49 µm(48-49) wide. Caudal alae of bursa and spicules (75 µm in length) were well developed. Eggs: The oval shaped eggs in the female uterus, when cultured, were 66 × 56 µm in size, and the eggs laid by the adult could not be detected. So, reproduction might be through to be ovoviviparity. The five cases were re-examined during the period from the 1st to the 3rd week after stool examinations, but Rhabditis sp. were detected again in 4 cases in 1st week. When they were examined in 3rd week, larvae could not be detected . So, it was thought that the infection of Rhabditis sp. to humans was facultative.