The in-vivo activity of imipenem against VIM-1-producing Klebsiella pneumoniae (VPKP) was assessed in a thigh infection model in neutropenic mice. Animals were infected with three VPKP isolates (imipenem MICs 2, 4 and 32 mg/L, respectively) and a susceptible clinical isolate (MIC 0.125 mg/L) that did not produce any beta-lactamase with broad-spectrum activity. Bacterial density at the site of infection was determined after imipenem treatment (30 and 60 mg/kg every 2 h for 24 h). The log(10) reduction in CFU/thigh was greatest for the wild-type isolate, intermediate for the two imipenem-susceptible VPKP isolates, and lowest for the imipenem-resistant VPKP isolate. Whilst in-vivo imipenem activity appeared reduced against in-vitro susceptible VIM-1 producers compared with a VIM-1-negative control, an increased drug dosage could moderate this reduction.