Spontaneous bacterial peritonitis (SBP), a common complication of cirrhosis of liver, might result from translocation of bacteria from the small bowel. However, there is scanty data on frequency of small intestinal bacterial overgrowth (SIBO) in patients with cirrhosis of the liver. There are no data on SIBO in patients with extra-hepatic portal venous obstruction (EHPVO) in the literature. A total of 174 patients with cirrhosis of the liver, 28 with EHPVO and 51 healthy controls were studied for SIBO using glucose hydrogen breath test (GHBT). Persistent rise in breath hydrogen 12 ppm above basal (at least two readings) was considered diagnostic of SIBO. Of 174 patients (age 47.2 +/- 11.9 years, 80.5% male) with cirrhosis due to various causes, 67 (38.5%) were in Child's class A, 70 (40.2%) class B and 37 (21.7%) class C. Of the 174 patients with cirrhosis, 42 (24.14%) had SIBO as compared to 1 of 51 (1.9%) healthy controls (P < 0.0001). Patients with EHPVO had similar frequency of SIBO compared to healthy controls [2/28 (7.14%) vs 1/51 (1.97%), P = ns]. Frequency of SIBO in Child's A, B and C was comparable [13 (18.6%) vs 16 (23.9%) and 13 (35.1%), respectively; P = ns]. Presence of SIBO were not related to ascites, etiology of cirrhosis, and degree of liver dysfunction. SIBO is common in patients with cirrhosis of the liver. Patients with EHPVO do not have higher frequency of SIBO than healthy subjects. SIBO in cirrhosis is not related to the degree of derangement in liver function or of portal hypertension.