Background/Aims: Spontaneous bacterial peritonitis is one of the most common complications attending the onset of ascites in patients with liver cirrhosis. The aim of this study was to demonstrate whether it is possible, on the basis of ascitic fluid polymorphonuclear cell count in patients with liver cirrhosis and spontaneous bacterial peritonitis, to determine the optimal duration of cefotaxime therapy, as the most frequently applied empirical therapy, and possibly anticipate the disease recurrence. Methodology: In 16 patients with alcoholic liver cirrhosis and confirmed diagnosis of spontaneous bacterial peritonitis, cefotaxime therapy was administered 2g t.i.d. during 5 days. Before the therapy, at 48 hours, 5 days and 15-20 days after the cefotaxime therapy was started, in all patients with spontaneous bacterial peritonitis diagnostic abdominal paracentesis was performed, each time determining the ascitic fluid polymorphonuclear cell count together with microbiological analysis. Results: In the course of the "primary" spontaneous bacterial peritonitis attack, 3 patients died (18.8%). In 4 patients the recurrence of spontaneous bacterial peritonitis was observed within 15-20 days after therapy was discontinued. Two patients died during the therapy of spontaneous bacterial peritonitis recurrence. After 48 hours of therapy, 11 patients with the "primary" spontaneous bacterial peritonitis attack were without any symptoms (68.8%). Out these 11, 10 patients (62.5%) had the ascitic fluid polymorphonuclear cell count lower than 250/mm3. After 5 days of therapy, 12 patients (75%) were free of symptoms, and the number of ascitic fluid polymorphonuclear cell count <250/mm3 was still found in 10 (62.5%) patients. No association between the presence of symptoms 48 hours after the therapy and the recurrence of spontaneous bacterial peritonitis was established. A significant association was found between the ascitic fluid polymorphonuclear cell count determined 48 hours after the therapy and the recurrence of spontaneous bacterial peritonitis. A recurrence occurred in only 1 patient with the number of ascitic fluid polymorphonuclear cell count <250/mm3, 48 hours after the therapy was started. A recurrence of spontaneous bacterial peritonitis occurred in all the patients who had an ascitic fluid PMN cell count >250/mm3, 48 hours after the the therapy was started. Conclusions: By monitoring the ascitic fluid PMN cell count it seems to be possible to determine efficacy and optimal duration of cefotaxime therapy in patients with spontaneous bacterial peritonitis when it is of most importance that the number of asctic fluid PMN cell count should decrease below 250/mm3 during the therapy.