Measured and compared the behavior characteristics and security scores of 35 infants (6-24 months) treated with extinction for sleep disturbance with those of 13 untreated and 15 normal sleep controls. There was no evidence of detrimental effects on the treated infants whose security, emotionality/tension, and likeability scores improved. The findings are congruent with those from a previous study with preschoolers and have important implications for the prevention of later behavior problems in sleep-disturbed children.