Fifty-two (41 females, 11 males) overweight patients, mean body mass index (BMI) = 29.3, were treated for 6 months in a randomized, double-blind, placebo-controlled, parallel group design. The treatment consisted of an energy restricted diet and a dietary fibre supplement amounting to 7 g/day. After treatment the weight reduction in the fibre-treated group, 5.5 +/- 0.7 kg, was significantly higher than that of the placebo group, 3.0 +/- 0.5 kg (P = 0.005). Both groups were normotensive and comparable commencing treatment, 126.5/75.6 +/- 2.0/1.3 mm Hg versus 126.7/78.7 +/- 2.5/1.6 mm Hg. The treatment changed blood pressure non-significantly. Hunger feelings using visual analogue scales (VAS) were significantly reduced from 139.8 +/- 8.2 cm to 118.3 +/- 7.0 cm in the fibre-treated group, whereas a significant increase from 129.5 +/- 6.9 cm to 146.9 +/- 8.8 cm (P less than 0.02) was seen in the placebo group. Side-effects were predominantly gastrointestinal and equally distributed in the two groups. It is concluded that a dietary fibre supplement is of value in the management of overweight, enhancing weight loss and decreasing hunger feelings.