defined by the presence of ≥250 polymorphonuclear cells (PMN)/mm 3 in ascites in the absence of an intra-abdominal source of infection or malignancy. It is the most common bacterial infection in cirrhosis, accounting for 10%-30% of all reported bacterial infections in the patients admitted to hospital. [1-3] In outpatients without symptoms, the prevalence is low (3.5% [4] or lower [5, 6]), but in the nosocomial setting, the prevalence increases, ranging from 8% to 36%. [7,8] SBP is diagnosed when (a) the ascitic fluid culture grows pathogenic bacteria (almost always pure growth of a single type of organism), (b) the ascitic fluid neutrophils count is ≥250 cells/mm 3 , and (c) there is no evidence of surgically treatable intra-abdominal sources of infection. Depending on the culture and cell count ascitic fluid results, SBP has been classified into two variants [8] : Background: Spontaneous bacterial peritonitis (SBP) is the development of a monomicrobial infection of ascitic fluid in the absence of any contiguous source of infection. It occurs most commonly in conjunction with cirrhosis of the liver and alcoholic liver diseases. Majority of the SBP cases are caused by gram-negative organisms, mostly Escherichia coli. Objective: To isolate the various bacteriological agents from ascitic fluid from clinically suspected cases of SBP and to determine their antibiotic sensitivity pattern. Materials and Methods: In this study, 217 ascitic fluid samples from clinically suspected cases of SBP were collected from December 2011 to November 2012. Ascitic fluid was collected by bedside tapping in blood culture bottle aseptically and immediately sent to a microbiology laboratory, Sir T Hospital, Bhavnagar, Gujarat, for microbiological examination. Bacterial examination and antibiotic sensitivity tests were carried out by standard microbiological techniques. Results: Of 217 clinically suspected cases of SBP, 71 (43.80%) had ascitic fluid polymorphonuclear cells (PMN) count ≥ 250/mm3. Among 71 cases, 31 (43.6%) cases were culture positive and 40 (56.4%) cases were culture-negative neutrocytic ascites. From 31 culture-positive cases, E. coli was isolated from 17 (54.9%) cases; Klebsiella spp. was isolated from 5 (16.2%) cases; Staphylococcus aureus was isolated from 6 (19.3%) cases; and Pseudomonas aeruginosa was isolated from 3 (9.6%) cases. All isolates were sensitive to cefotaxime and ceftriaxone. Conclusion: If diagnosed early, SBP can be treated with high success rate, thus ascitic fluid laboratory analysis including culture of all suspected patients will help in improving prognosis of the patients.