purpose: The purpose of this study was to evaluate the use of sorbitol as an inexpensive alternative to lactulose for treating constipation in the elderly. patients and methods: Thirty men aged 65 to 86 with chronic constipation were studied in a randomized, double-blind, cross-over trial in which lactulose and 70% sorbitol (0 to 60 mL daily) were each given for 4 weeks preceded by a 2-week washout period. results: The average number of bowel movements per week was 6.71 with sorbitol and 7.02 with lactulose (95% confidence interval of the difference: -0.43 to 1.06), and the average number of days per week with bowel movements was 5.23 with sorbitol and 5.31 with lactulose (95% confidence interval of the difference: -0.32 to 0.48). Eleven patients stated a preference for sorbitol, 12 for lactulose, and seven had no preference. On a visual analogue scale measuring severity of constipation (0 to 100 mm), the average score for sorbitol was 35.6 mm versus 37.1 mm for lactulose (95% confidence interval of the difference: -6.4 to 9.3). The sorbitol and lactulose treatment periods were also similar in percent of bowel movements recorded as "normal," frequency and severity of symptoms such as bloating, cramping, and excessive flatulence, and overall health status as assessed by a previously validated five-category questionnaire. There were no significant differences between sorbitol and lactulose in any outcome measured except nausea, which was increased with lactulose (p <0.05). conclusion: These results support the hypothesis that sorbitol and lactulose have no clinically significant differences in laxative effect. Sorbitol can be recommended as a cost-effective alternative to lactulose for the treatment of constipation in the elderly.