In a double-blind, multicenter trial, 502 patients hospitalized with community-acquired pneumonia were randomized to receive therapy with either ertapenem or ceftriaxone (for each, 1 g given intravenously once daily). After a minimum of 3 days, therapy could be switched to oral amoxicillin-clavulanate. The median duration of intravenously administered therapy for the 383 clinically evaluable patients was 4 days for both treatment groups; 345 patients (90.1%) had their treatment switched to orally administered therapy. Of the clinically evaluable patients, 168 (92.3%) in the ertapenem group and 183 (91.0%) in the ceftriaxone group had a favorable clinical response. Streptococcus pneumoniae was the most commonly isolated pathogen, and high cure rates were observed both for penicillin-susceptible and -nonsusceptible infections in the ertapenem group (28 [87.5%] of 32 patients versus 17 [100%] of 17 patients, respectively). Both treatment regimens were generally well tolerated; the most common drug-related adverse events reported were diarrhea (2.9% versus 2.7%) and nausea (0.8% versus 2.0%) in the ertapenem and ceftriaxone groups, respectively. These results suggest that ertapenem and ceftriaxone therapy have similar efficacy and safety in hospitalized patients with community-acquired pneumonia.