--Disease Characteristics-- Healthy term infants or infants at high epidemiologic risk for SIDS meeting one of the following criteria: Apnea of infancy Siblings of SIDS victim Preterm infants --Prior/Concurrent Therapy-- All study groups: No home treatment with supplemental oxygen, bronchodilators, diuretics, steroids, or respiratory stimulants other than methylxanthines Healthy term infants: No prior/concurrent medications or treatments except: Vitamins Eye prophylaxis Vaccines --Patient Characteristics-- All study groups: No concurrent pneumonia No history of congenital heart disease Current asymptomatic PDA or ASD, or small muscular VSD, not requiring treatment are allowed No ventriculoperitoneal shunt No home anticonvulsant therapy No congenital brain anomalies documented by head ultrasound, CT, or MRI No gastroesophageal reflux being treated by medication No midfacial hypoplasia or cleft palate No prior inborn error of metabolism (including MCAD or carnitine deficiency) No caregiver currently using illicit drugs No language barrier between researcher and caregiver Must have telephone in the home Healthy term infants: Gestational age at birth of 38-42 weeks Age no greater than 30 days postnatally for planned monitor start date Not admitted to a special care nursery Nursery discharge on/before date of maternal discharge or 48 hours of age, whichever is later No history of apnea or apparent life threatening event (ALTE) No history of SIDS in full or half siblings No history of SIDS in cousins, aunts, and uncles in the last 10 years 1 minute APGAR at least 4 5 minute APGAR at least 7 Apnea of infancy: Diagnosed ALTE (during sleep or awake) characterized by color change, muscle tone change, and apnea requiring intervention No specific etiology for the ALTE after a thorough diagnostic evaluation At least 12 hours of age and less than 6 months postnatal age when ALTE occurred Greater than 34 weeks gestation Weight greater than 1750 g Siblings of SIDS victim Half or full sibling of at least one previous SIDS victim Less than 1 month postnatal age at study entry Autopsy report confirmed SIDS in sibling Preterm infants Birth weight less than 1750 g Gestational age no greater than 34 weeks Postnatal age less than 120 days at time of hospital discharge