A review. On page 3, the Abstract is incorrect. The correct abstract should read: "This year (2007) marks the 50th anniversary of 6-aminopenicillanic acid (6-APA), the precursor of all semi-synthetic penicillins. This review, by a scientist who played a major part in the discovery and a physician who participated in the early clin. trials of these antibiotics, tells the story of the discovery and of the early development of the β-lactam antibiotics that revolutionized the treatment of infections.".