Introduction. Spontaneous bacterial peritonitis (SBP) is a common, severe complication of decompensated liver cirrhosis. Despite a standardized diagnostic protocol, detection of SBP is usually delayed, which increases the risk of mortality in these patients. This article is a literature review intended to highlight the appropriate diagnosis of SBP. Materials and methods. We have reviewed papers on the diagnosis of SBP, using the Google Academic search engine, the PubMed and ScienceDirect (Elsevier) databases. Results. Gold standard in the diagnosis of SBP is based on the counting of polymorphonuclears (PMN) with a cutoff of >250 cells/mm3 in the ascitic fluid with or without a positive culture. Clinical awareness is essential in identifying candidates at increased risk of SBP, such as those with low protein in ascitic fluid, history of upper gastrointestinal bleeding, administration of proton pump inhibitors. It is recommended to perform diagnostic paracentesis in the first 6 hours after hospitalization for all patients with cirrhosis and ascites, especially those with a recent history of upper bleeding, encephalopathy, acute kidney injury, progression of liver failure. Several simple scores and useful markers in the detection of SBP have been evaluated, such as procalcitonin, Il-6, lactoferrin, calprotectin, leukocyte esterase reagent test with the prospect of simplifying and speeding up the diagnosis. Conclusions. Diagnostic paracentesis and PMN counting represents the standard technique for SBP confirmation. Although with good performance, non-invasive markers have not proved their applicability. Further clinical studies are necessary for their validation.