The reasonable data on the basis of a PK/PD theory in clinical practice would be provided by the analysis in consideration of renal function because the excretion of meropenem mainly occurs from kidney. We carried out the simulation with pharmacokinetics of meropenem in consideration of renal function, and investigated whether renal function would affect Time above MIC (T>MIC). The % T>MICs were 18.9%, 35.0%, 49.4%, 61.1% in serum creatinine level 0.5, 1.0, 1.5, and 2.0 mg/dL, respectively, when MIC of causative organism was assumed to 4microg/mL. Furthermore, we investigated the association between renal function and clinical efficacy in three patients with peritonitis, who received meropenem. We conclude that the simulation in consideration of renal function would be useful in PK/PD-based analysis, and would give the clinically useful data in clinical practices.