Loneliness and perceived social support were examined in 39 adolescent boys with autism spectrum disorders (ASD) by means of a self-labeling loneliness measure, the UCLA Loneliness Scale (third version), and the Social Support Scale for Children. Twenty-one percent of the boys with ASD described themselves as often or always feeling lonely. Compared with 199 boys from regular schools in a national probability study, ASD was strongly associated with often or always feeling lonely (OR: 7.08, p less than 0.0005), as well as with a higher degree of loneliness ("F"(1,229) = 11.1, p less than 0.005). Perceived social support from classmates, parents, and a close friend correlated negatively with loneliness in ASD. The study, therefore, indicates a high occurrence of loneliness among adolescent boys with ASD and points at perceived social support as an important protective factor.