Patients with bacterial overgrowth of the small intestine developed spontaneous bacterial peritonitis (SBP) more frequently than patients without bacterial overgrowth of the small intestine. The objective of this study was to determine whether the incidences of small intestine dysmotility and bacterial overgrowth are higher in cirrhotic patients with a history of SEP than in cirrhotic patients without SEP: Forty cirrhotic patients were enrolled in this study. There were 20 patients with a history of SEP and 20 patients without a history of SEP. Small intestine bacterial overgrowth was diagnosed by breath hydrogen test. Small intestine motility was recorded, by a 3-channel solid-state manometric catheter, for 24 hours. There were no statistical differences in age or sex between the two groups. The Child-Pugh scores in the SEP group were higher than in the non-SEP group (10.5 +/- 2.1 vs. 8.1 +/- 1.9, P <.01), The incidence of bacterial overgrowth of the small intestine was higher in the SEP group than in the non-SEP group (70% vs, 20%, P <.01), The amplitude and duration of migrating motor complex (MMC) activity fronts, as well as the number of clusters per hour, were similar in both groups. However, the frequency of MMC activity fronts was higher in the non-SEP group than in the SEP group (4.8 +/- 2.3/24 hours vs. 3.5 +/- 1.2/24 hours, P <.05), In addition, the MMC velocity was significantly higher in the non-SEP group (8.3 +/- 2.6 vs. 5.3 +/- 2.1 cm/min, P <.01), The incidence of bacterial overgrowth of the small intestine was higher in cirrhotic patients with history of SEP than in those without SEP. Small intestine motility dysfunction was more severe in cirrhotic patients with history of SEP: Impaired motility of the small intestine, causing bacterial overgrowth of the small intestine, may be one of the explanations for recurrent SEP in cirrhotic patients.