Preterm labor and delivery continues to be one of the most serious problems in obstetrics, both medically and socioeconomically. The more classically used definitions of preterm delivery may not be useful in this era of advances in neonatal care. Similarly, the classically used criteria for "success" in tocolysis may obscure benefits from prolongation of gestation that does not meet these criteria. This article reviews the etiologic theories, risk factors, diagnostic techniques, and possible primary and adjunctive modes of therapy for preterm labor. The emphasis of these recommendations is on their clinical utility for the practicing obstetric care provider.