Substantial variation in childcare arrangements exists both within and between populations. Research has suggested negative stress-related outcomes for children who regularly attend daycare facilities. In the present study, 122 cortisol and 94 secretory immunoglobulin A (SIgA) samples from 32 British children aged between 3 and 8 were analyzed using multilevel modeling to assess effects of daycare attendance and other childcare- related variables on children's stress and SIgA immune function. Parents' reports of children's aggression andfamily discord within 2 hr of saliva collection were associated with elevated cortisol levels in children. With these acute stressors statistically controlled, retrospective data on parent-child cosleeping showed that children who had coslept in their parent(s) room had lower cortisol levels, as did children who had attended less daycare in the first 4 years of life. The parenting- related variables did not predict SIgA immunity. The results are discussed in the context of theories of parenting strategies. (c) 2007 Wiley Periodicals, Inc.