An interview-based rating scale consisting of 15 items for assessment of gastrointestinal symptoms in irritable bowel syndrome and peptic ulcer disease has been developed. The interrater reliability was estimated by means of independent and simultaneous duplicate ratings by two raters in 20 cases and ranged from 0.86 to 1.00. The scale was easy to apply and proved to be useful in comparing the effectiveness of different modes of treatment in two clinical trials.