The tolerability of the 2 most frequently used carbapenems, imipenem/cilastatin and meropenem, is reviewed. Both of these drugs, but especially imipenem, are potentially neurotoxic and may cause seizures if overdosed relative to renal function and/or bodyweight. The therapeutic margin is considerably narrower with imipenem/cilastatin which cannot be given at doses required for treatment of bacterial meningitis. Meropenem on the other hand, is considerably less prone to cause seizures and its tolerability and efficacy are well documented in 3 relatively large, controlled studies in adults and children with meningitis. They showed that meropenem was as effective and well tolerated as cefotaxime or ceftriaxone. Another potential advantage of meropenem over imipenem/cilastatin is that it can be given intravenously at a high rate without increased risk of nausea or vomiting. An obvious reason for using a carbapenem instead of a cephalosporin for empirical treatment of life-threatening infections is that both imipenem/cilastatin and meropenem have a broader spectrum of activity. They are also more resistant to hydrolysis by the most common beta-lactamases, including the class I cephalosporinase frequently produced by Enterobacter spp. and Pseudomonas spp. and the extended spectrum enzymes, now commonly found in Escherichia coli and Klebsiella spp.