Circumscribed interests are a fascinating and an understudied phenomenon in some individuals with autism spectrum disorders (ASD). Research in this area is likely to contribute to our understanding of ASDs and to advancing developmental knowledge on learning processes used to adapt to the demands of everyday social life. This study reports on a survey of special interests in 96 children and adolescents with higher functioning ASD. The survey included listing of up to three special interests for each child, and the rating of level of interference of a given interest upon children's activities when by themselves and when in contact with family members, peers, and other adults. This information was collected for both preschool and elementary school years. Special interests were classified into eight categories in terms of their nature (rather than topic), which included the ways through which the interest was manifest and pursued. Results indicated that circumscribed interests (a) are the norm rather than the exception in this population (75% and 88% of the sample for the younger and the older age periods, respectively), (b) most frequently involve verbal learning and memorization of facts (65% and 81% for the younger and the older age periods, respectively), (c) often involve an element of interest in letters and numbers in the preschool years (35% of the sample), (d) greatly interfere with activities pursued by oneself or with others, and (e) level of interference is predictive of lower social and communicative adaptive behavior later in life. Given the ubiquity of circumscribed interests in this population, their verbal nature, and the passion that children with ASD invest in these pursuits, we suggest the need for studies that will trace the longitudinal course of learning profiles from early childhood and possible interventions that may address these areas. The following are appended: (1) A sample of the over 250 exemplars of circumscribed interests exhibited by the individuals with higher functioning autism spectrum disorders; and (2) Sample Page from Yale Special Interests Survey. (Contains 1 table and 1 figure.)