To evaluate the in vitro antimicrobial activity of panipenem/betamipron. The minimal inhibitory concentrations (MIC) of panipenem/betamipron against 247 clinical isolates was determined by agar dilution method.Compared with 5 other antimicrobial agents, the activity of panipenem against Haemophilus influenzae , Staphylococcus aureus containing methicillin resistant Staphylococcus aureus (MRSA) and Escherichia coli was slightly superior to that of imipenem; however, its antibacterial activity against Pseudomonas aeruginosia was about 1/4 that of imipenem. The antimicrobial activity of panipenem and imipenem against Gram negative bacteria such as Klebsiella pneumoniae and Enterobacter spp was slightly inferior to meropenem, superior to that of ceftazidime, cefoperazone/sulbactam and oxacillin. The activity of panipenem was affected by the inoculum size, pH of medium and adding of serum. Panipenem was the feasible antibiotics in treating hospital acquired infection caused by multi resistant bacteria, and the severe mix infections of aerobic and anaerobic bacteria.