Penicillin is generally regarded as the preferred drug for treatment of anaerobic lung abscess. This consensus is reflected in recent authoritative texts dealing with internal medicine (1), infectious diseases (2), chemotherapy (3), and pulmonary disease (4). "Penicillin" was the "right" answer for the query regarding the preferred drug for primary lung abscess in the 1982 examination of the American Board of Internal Medicine. Notwithstanding such conventional wisdom, in this issue Levison and associates (5) present data suggesting that clindamycin therapy is superior. The findings in this comparative trial, and especially the high rate of penicillin failures, run counter to current