Apnea of prematurity is a common problem of the premature infant under 30 weeks gestation. Theophylline and caffeine, two methylxanthines, are widely used to treat this condition. The drugs are equally effective in preventing apnea in the premature infant. Caffeine citrate has many advantages over theophylline, however, including once-a-day dosing, more predictable plasma concentrations, earlier onset of action, and minimal side effects. Caffeine is therefore the initial drug of choice for apnea of prematurity.