In the current study we examined the links between maternal sensitivity and children's secure attachment in a sample of 45 preschool-age boys with Autism Spectrum Disorders (ASD). We hypothesized that mothers of securely attached children would be more sensitive to their children than mothers of insecurely attached children. Children's attachment was assessed using Ainsworth's Strange Situation Procedure (SSP; Ainsworth, Blehar, Waters, & Wall, 1978). Mothers' sensitivity and children's responsiveness to their mothers were assessed using the Emotional Availability Scales (Biringen, Robinson, & Emde, 1993). The findings supported our hypothesis: mothers of securely attached children were more sensitive to their children even when controlling for the severity of children's diagnosis (Autism Disorder vs. Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS)), children's level of functioning (high vs. low), and children's levels of responsiveness. The significance of sensitivity for security of attachment in ASD and the implications of these findings for the validity of the SSP in children with ASD are discussed.