Research of features of a current of a spontaneous bacterial peritonitis (SBP) allows to allocate close interrelation between SBP, system inflammatory reaction and a sepsis to consider SBP, as one of stages in evolution of the difficult infectious process caused, as a rule, by resident flora, developing at patients with decompensated liver cirrhosis (LC), which demands timely preventive maintenance and adequate antibacterial therapy. In the present work therapy and preventive maintenance SBP questions are considered. In article the extensive review of the data of the literature and own supervision by efficiency of treatment SBP also is presented. For the purpose of optimization of pharmacotherapy of the sick LC, the complicated ascites, had been conducted pharmacokinetics research ciprofloxacin (CPF) according to dynamics of its maintenance in blood serum (BS) and ascitic fluid (AF) depending on presence and ascites size. Materials and methods. Researches are spent 18 sick decompensated liver cirrhosis (a class B and C on Ch-P), without signs SBP after unitary reception of 500 mg CPF per os on an empty stomach. All patients have been divided on two groups: I gr. (n = 10) with the expressed, intense ascites (> 10 1) and II gr. (n = 8) with the moderate, small ascites. Definition CPF in BS also was already carried out by a method of a highly effective liquid chromatography. On the basis of the received data for each patient counted the semidelucing period (T1/2), the area under pharmacokinetic curve (curve concentration - time) - (AUC), volume of distribution of a preparation (Avd), factor AUC(AF)\MIC (size of the relation of the area under pharmacokinetic curve to its minimum inhibitive concentration). Results of research have shown that concentration levels (C) (CPF in BS and AF for the given concrete patient are at one level, showing thus distinctions in dynamic behavior. Average value AUC(AF)\MIC (MIC - minimum inhibitive concentration) at patients II gr. has made 187,3 +/- 5,6 h that almost in 2 times more than necessary value, as has allowed not to recommend to patients increase in dose CPF. On the contrary, parity AUC(AF)/MIC at patients I gr. has made 43,8 +/- 3,6 h (less than 100 h) that it is not enough for therapeutic effect. Conclusions. The conducted research has allowed to make the conclusion that presence and ascites size make essential impact on pharmacokinetic parameters CPF and to recommend increase in dose CPF to 1000 mg/days for sick LC with sharply expressed ascites and safe nephritic function.