Treatment of the following infections when caused by susceptible organisms: Upper and lower respiratory tract infections. Skin and soft tissue infections. Conjunctivitis of the newborn caused by chlamydia trachomatis. Urogenital infections caused by chlamydia trachomatis. Venereal diseases (as an alternative regimen to penicillins and tetracyclines). Intestinal amebiasis. Legionnaires' disease. Long-term prophylaxis in rheumatic fever. Short-term prophylaxis against bacterial endocarditis in patients hypersensitive to penicillin who have congenital heart disease or rheumatic or other acquired valvular heart disease when undergoing dental procedures and surgical procedures of the upper respiratory tract. Enteric infections caused by Campylobacter jejuni.