A multicentre study was carried out in general practice to investigate the efficacy, safety and tolerance of cephalexin in the treatment of infections in 194 patients with an underlying chronic disease or other complications, and in patients over the age of 65 years. For comparison, a group of 145 patients with no such complicating conditions was included in the study. Altogether, 339 patients were treated with doses of 1 g or 2 g cephalexin daily depending on the type and severity of infection. After treatment for 5 days, over 80% of patients were cured or much improved, with no differences between the two groups. Of the 95 patients who received 10-days' treatment, the clinical outcome was considered satisfactory in approximately 80% in both groups. No clinically significant biochemical changes were recorded, no drug interactions with concurrent therapy were reported, and the incidence of side-effects was low.