Twenty-three infants aged 6 days to 9 months, sequentially referred for apnea or apparent life-threatening events (ALTE), were studied. A selective approach consisting of hospitalization, prolonged cardiorespiratory monitoring, and a graduated investigative protocol yielded positive findings in 75% of the subjects. Polysomnographic study and continuous esophageal pH monitoring were found to be the most informative. In addition to other appropriate therapeutic interventions, cardiorespiratory home monitoring was prescribed for four patients. In three nonmonitored subjects apnea recurred. Two infants died, one with homocystinuria complicated by brain hemorrhage and another with a fulminant viral infection. These investigative results and their outcome indicate that in cases of apnea or ALTE in apparently healthy infants, in-patient monitoring and evaluation is of much value. Home monitors should only be recommended in a selected group of patients, and an adequate follow-up and support system is essential.