Spontaneous bacterial peritonitis is caused by infection of ascitic fluid without any apparent intraabdominal source of infection. The disease most commonly occurs in patients with cirrhosis and 70% of cases of infections are caused by pathogenes from gastrointestinal tract. The article presents the case of 38-year-old patient with spontaneous peritonitis who was treated surgically. The primary nature of the disease was confirmed by laparotomy and bacteriological examination results (Streptoccocus pneumonia) of ascitic fluid. After 54 days of hospitalisation and undergoing re-laparotomy, he was discharged in good condition.