Amoxicillin is an aminopenicillin available in the United States only for oral use. It has an antibacterial activity and spectrum similar to that of ampicillin and is destroyed by gram-positive and gram-negative beta-lactamases. It is more active against enterococci and salmonellae than ampicillin, but less active against Shigella. It is better absorbed than ampicillin from the gastrointestinal tract with blood levels two to two and one half times those of ampicillin. Amoxicillin is an excellent agent to treat otitis media, bacterial sinusitis, bacterial exacerbations of bronchitis, acute lower-urinary-tract infections, gonorrhea, and typhoid. In special settings it may be useful as oral therapy of endocarditis, septic arthritis, and osteomyelitis and as prophylaxis to prevent endocarditis. When the cost of amoxicillin approaches that of ampicillin, it should replace that agent as the oral aminopenicillin of first choice.