Spontaneous bacterial peritonitis (SBP) is a potentially life-threatening complication of ascites diagnosed by paracentesis. We determined predictors of SBP to facilitate patient selection. The 301 paracenteses performed in 119 patients (51 women, 68 men) from July to November 2015 were retrospectively reviewed. Presentation, lab data, depth of the deepest ascites pocket on ultrasound, total volume of ascites removed, absolute neutrophil count, and complications were studied. Of 301 paracenteses, 16 (5%) diagnosed SBP. On univariate analysis, SBP was associated negatively with history of cirrhosis and positively with history of cancer, abdominal pain, greater depth of the fluid pocket, prior SBP, and leukocytosis. Multivariate analysis using these variables to predict SBP was significant (P < 0.0001); only depth of the largest fluid pocket (P = 0.008) and complaint of abdominal pain (P = 0.006) were independent predictors. Receiver-operator curve analysis showed that a 5-cm cutoff of pocket depth yielded 100% sensitivity and 32% specificity. Two (0.1%) hemorrhagic complications occurred, one causing death and one necessitating laparotomy. In conclusion, deeper ascites pockets and abdominal pain are independent predictors of SBP. When the largest ascites pocket is <5 cm, the probability of SBP is nearly negligible. Given the potential for hemorrhagic complications, findings may help triage patients for paracentesis.