The aim of the study was to investigate whether galacto-oligosaccharides (GOS) relieve constipation in elderly people. The final study population consisted of 14 female subjects, mean age 79.6 (69–87) years, who suffered from constipation. The study was a double-blind two-period cross-over study. Both study periods lasted 2 weeks. The subjects ingested either 2 control yoghurts or 2 GOS-containing yoghurts daily. The yoghurts were otherwise similar, but the daily dose of GOS (Elix’or, BWP, Holland) from the GOS yoghurt was 9 g. The regular use of laxatives was stopped during the study periods and laxatives were used only when necessary. All the subjects reported the function of their intestines daily in a questionnaire. The defecation frequency per week (mean, range) was higher during the GOS period (7.1, 3–15) than during the control period (5.9, 1–14). GOS had no statistically significant effect on the use of laxatives, the consistency of feces or the ease of defecation, although GOS seemed to make defecation easier (p = 0.07). The adverse gastrointestinal symptoms were similar during both the control and the GOS periods. GOS seem to relieve constipation in most elderly people but the responses differ individually.