263 hospitalized patients were enrolled in a multicentre study to assess efficacy and safety of i. m. meropenem, compared to ceftazidime, in the treatment of lower respiratory tract infections and urinary infections as well. Meropenem, administered at a dose of 500 mg tid, was therapeutically equivalent to the reference agent (1000 mg tid in RTI's and 500 mg tid in UTI's) in both indications. The two treatments were well tolerated, without any serious local or systemic side effect.