OBJECTIVES: To evaluate the clinical-economic value of ertapenem therapy in patients with complicated abdominal infections (CAI) vs. standard combination therapy considering the development of bacterial resistance in the Russian settings METHODS: The pharmacoeconomic analysis utilized the cost-effectiveness analysis (CER). If the efficacy and the cost of any of the studied regimens exceeded those of the other regimen, an incremental analysis was carried out (ICERs). The decision analytic model was based on the clinical studies of CAI treatment. Efficacy and safety data were based on additional analyses of a randomised, double blind, multinational trial of ceftriaxone plus metronidazole, ciprofloxacin plus metronidazole, ertapenem. For the assessment of the effects of secondary bacterial resistance on treatment efficacy in CAI we utilized results obtained with a “susceptible – infected – susceptible” model  (SIS-model) for development of antimicrobial resistance (i. e. reduction of the susceptibility /effectiveness ratio observed with time), for ceftriaxone / metronidazole, ciprofloxacin / metronidazole, ertapenem. To evaluate the degree of inaccuracy of the results, sensitivity analyses were performed.  RESULTS: It was established that the mode of starting treatment of CAP combination therapy ciprofloxacin / metronidazole was more expensive ($3153) in comparison with the use of ertapenem ($2860) and ceftriaxone/metronidazole ($2579). The CER established that the mode of starting treatment of CAP with ertapenem was both more effective and less expensive in comparison with the use of ciprofloxacin / metronidazole. The SIS-model showed that sensitivity to ertapenem bacterial agent is kept significantly longer then to ceftriaxone / metronidazole and ciprofloxacin / metronidazole  (up to 60 month).The analysis of the alternative, whose cost of treatment of CAR was equal in all groups, has shown that the strategy using ertapenem was dominating. CONCLUSIONS: At CAI, such as a secondary peritonitis when the basic activators are Escherichia ñoli, Klebsiella pneumoniae and Bacteroides Fragillis it is more expedient to begin treatment with ertapenem.