To examine the prevalence and clinical assessment of sighs in neonates, we observed three different patterns of sighs: (A) sighs in the absence of apneic pause; (B) sighs with instantly following apneic pause >2 s, and (C) sighs with apneic pause >2 s following 1–3 normal breaths. We investigated preterm and term infants with 12 h nocturnal polygraphic recording. Sighs were more frequent in preterm than in term infants and more so during REM sleep than non-REM sleep. The part of sighs B of total number of sighs increased with gestational age. During REM sleep sighs without apnea were predominant, whereas apnea-associated sighs were mainly found during non-REM sleep.