The purpose of this study was to examine bowel habits, dietary habits, and nutrient intake of constipated adults, and the effects of prune products on relieving constipation symptoms. Fifty one adults with self-reported constipation (mean age 23 years, range 19-41 years, 10 males and 41 females) participated in this study. After a baseline survey on bowel habits and dietary habits, participants were asked to consume at least 50 g of prune and 200 ml of prune juice per day during a 4-week period in addition to usual diet. Nutrient intake was estimated by a 24 hour recall at the baseline and once every week by diet records during the intervention. Data were analyzed after classifying the subjects into mild constipation group and severe constipation group by the severity of the symptoms. During the intervention, the subjects with mild constipation consumed 56 g of prunes (about 5.6 fruits) and 200 ml of prune juice, and the subjects with severe constipation consumed 59 g of prunes (about 5.9 fruits) and 207 ml of prune juice. Average intakes of energy, dietary fiber and water of the subjects in the mild constipation and severe constipation group increased during the intervention compared to the baseline. Average dietary fiber intake of the mild constipation and severe constipation groups significantly increased from 12.5 g and 11.6 g at the baseline to 18.5 g and 16.8 g after consuming prune products, respectively. These changes were accompanied by an increase in the number of bowel movements, a decrease of defecation time, a change to a softer stool consistency, and a decrease of abdominal pain during defecation. Seventy two subjects answered that prune products were effective to improve their overall constipation symptoms. Our data show that supplementation of prune products is effective to provide energy, dietary fiber and water, and to relieve constipation symptoms for constipated adults.