We explored relations between children's sleep and levels of salivary interleukin-6 (IL-6). Children were healthy boys (n = 28) and girls (n = 36) who ranged in age between 8 and 9 years. Through actigraphy, the amount and quality of children's sleep was examined objectively in their homes for 1 week. Children also rated their Morningness/Eveningness predisposition and subjective sleepiness, and parents reported on their children's Sleep Disordered Breathing and Sleepiness. Children provided saliva samples before and after a series of cognitive/social tasks (an intelligence test, listening to a marital argument, and performing a star-tracing task), which were later assayed for IL-6. Children with higher salivary IL-6 levels reported increased Eveningness predispositions and their parents reported higher levels of Sleep Disordered Breathing. Furthermore, lower levels of sleepiness, longer sleep amount, and better quality sleep in children were each predictive of increased IL-6 reactivity from pre- to post-task conditions. The findings illustrate (for the first time to our knowledge) that sleep disruptions in otherwise healthy and normally developing children may be associated with individual differences in levels of IL-6 in saliva.