This analysis evaluated the association between sleep disturbance and gastrointestinal symptoms in women with and without irritable bowel syndrome (IBS), and examined the role of psychological distress in this relationship. Women with IBS (N = 82) reported considerably higher levels of sleep disturbance compared to controls (N = 35), using both retrospective seven-day recall and daily diary recall for two menstrual cycles (P < 0.05 on 8 of 10 measures). We used daily diary data to estimate the association between sleep disturbance and gastrointestinal symptoms, both across women (ie, whether women with high average sleep disturbance have higher average gastrointestinal symptoms) and within woman (ie, whether poorer than average sleep on one night is associated with higher than average gastrointestinal symptoms the following day). The regression coefficients for the across-women effect are large and highly significant in both groups (IBS, beta +/- SE = 0.46 +/- 0.08, P < 0.001; controls, 0.57 +/- 0.13, P < 0.001). The regression coefficients for the within-woman effect are considerably smaller and statistically significant only in the IBS group (IBS, 0.06 +/- 0.02, P = 0.006; control, 0.01 +/- 0.03, P = 0.691). These regression coefficients showed little change when daily psychological distress or stress was controlled for, the one exception being the coefficient for the across-women effect in the IBS group, which decreased substantially but still remained highly significant. Because it is possible that gastrointestinal symptoms could, in fact, cause poor sleep, we also fitted the temporally reversed model to evaluate the association between gastrointestinal symptoms on one day and sleep disturbance that night. The within-woman regression coefficients were nonsignificant in both the IBS and control groups. In conclusion, these results are consistent with the hypothesis that poor sleep leads to higher gastrointestinal symptoms on the following day among women with IBS.