Objective To derive reference curves of polysomnographic parameters for clinically healthy infants and children in the first and second year of life. Study design From January 1989 to December 1999 a total of 13 373 polygraphic sleep recordings were carried out at the sleep laboratory of the Vestische Kinderklinik Datteln, a tertiary referral centre for sleep-related respiratory problems in infants and children. In order to create a data base for reference curves, 681 recordings were retrospectively selected from the total pool, if the following criteria were fulfilled: first polygraphic sleep recording of the proband, clinically healthy term infants without symptoms of upper respiratory infection at the time of sleep study. Premature birth (< 37 weeks of gestation), low birth weight (< 2 500 g), apparent life-threatening events (ALTE), neonatal complications, known cardial, pulmonary, cerebral and metabolic disorders, dysmorphic syndromes, sudden infant death (SIDS) of a sibling, heavy parental smoking (> 10 cigarettes per day), and maternal drug addiction were exclusion criteria for the reference group. Recording and evaluation of polysomnographies were carried out according to published recommendations of the Pediatric Task Force of the German Sleep Society (DGSM). Results: Reference curves covering an age range of 1 to 24 months are presented for the following parameters: quiet and active sleep, coordinated and paradoxical patterns of thoracic and abdominal breathing movements, periodic breathing, frequency of respiratory pauses of ≤ 3 seconds, ≤5 seconds and ≤ 10 seconds duration, respectively, frequency, mean and maximal duration of respiratory pauses following a sigh, central, obstructive and mixed respiratory pauses, respectively, transcutaneous partial pressure of oxygen and carbon dioxide, oxygen... [ABSTRACT FROM AUTHOR]