In order to study the prevalence of constipation among female college students in Korean and the effect of yogurt, 3,243 students in Seoul area were surveyed by questionnaires for the status of stool evacuation and 197 students with possible constipation were sampled and fed apple yogurt II from Pasteur dairy Company for 3-weeks period. Students of constipation amounted to a high ratio of 53.4%, which consisted of 13.4% in heavy constipation (1-2 times evacuation per week) and 40.0% in mild constipation(3-4times evacuation per week) during the past one-year period. To 90 of heavy constipation and 107 of mild constipation students were fed 290ml of yogurt every morning for 3-weeks period and examined for the status of stool evacuation by subsequent after 1 weeks, 57.9% after 2 weeks and 60.4% after 3 weeks(p<0.05). The effect of improvement in stool frequency was greater in heavy group than in mild group through the 3-weeks period. The number of students who experienced the disappearance of inconvenience in evacuation after drinking the yogurt was 52.3% after 1 weeks, 72.1% after 2 weeks and 76.1% after 3 weeks. Discomfort such as stomach disorder and mild diarrhea during the drinking period was observed in 24% students and it appeared that a longer drinking period was needed stool frequency was 38.7% after 1 week and 37.6% after 1 month since discontinuing yogurt drinking. The number of students reverted to the previous habit of evacuation after discontinuing was 51.6% after 1 week and 63.5% after 1 month, which were not significantly different between heavy and mild groups(p>0.05).