Patients with spontaneous bacterial peritonitis (SBP) usually have serious complications associated with deteriorating synthetic and excretory function of the liver cells, and require hospitalization and regular monitoring of biochemical parameters in blood and ascites.Aims - to determine the average values of laboratory parameters in blood and ascites in patients with SBP, to determine whether there is a difference in the average values between patients with SBP and non-SBP as well as their predictive power for the diagnosis of SBP.The study was designed as a prospective-analytical-observational and was conducted at the University Clinic for Gastroenterohepatology in Skopje for a period of one year. The study population included hospitalized patients with established liver cirrhosis, regardless of etiology; 70 patients, divided into two groups, 35 patients with SBP and 35 non-SBP. The selection of patients who were included in the study was conducted according to pre-determined inclusion and exclusion criteria. All diagnostic test specimens were immediately referred to the Central Clinical Laboratory. Five ml of a total of 10 ml of ascites were used for automatic counting of PMNC, and 5 ml for biochemical analysis of ascites (total sweat-WP). At the same time, for the needs of biochemical blood tests, a venipuncture of 10 ml of blood was performed.The univariate analysis showed that INR, albumin/s, creatinine/s, TP/ascites (p=0.039, p=0.035, p=0.013, p=0.000, p=0.030) were independent risk factors for the development of SBP. INR>1.2 significantly increased the chance of SBP by three times (Exp (B) = 3.222 (CI (1.063-9.768)). Serum albumin<35 g/L significantly increased the chance of SBP by five and a half times (Exp (B) = 5.712 (CI (1.135-28.748). Creatinine/s>115 µmol/L significantly increased the chance of SBP by four times (Exp (B) = 4.070 (CI (1.352-12.255)).TP in ascites ≤10 significantly increased the chance of SBP by five times (Exp (B) = 5.337 (CI (6.243-416.469). The multivariate logistic analysis confirmed that INR>1.2 and creatinine>115 µmol/L were statistical risk factors (predictors) that increased the chance of SBP.Low serum albumin values are independent risk factors for predicting SBP and significantly increase the risk of developing SBP by five and a half times. Patients with SBP have lower mean TP values in ascites than non-SBP. Low TP values in ascites<11g/L are independent risk factors for the development of SBP and significantly increase the risk of SBP by five times. Of course, additional and larger studies are necessary in order to confirm our conclusion in the future.