Asperger syndrome has so far been the subject of very little systematic empirical inquiry. This paper reviews those few studies in the literature and some data from a new Swedish study which has reported findings pertinent to estimations of Asperger syndrome prevalence. It is concluded that among children with normal intelligence, rates of 10-26 per 10,000 children are minimum figures. Another 0.4 per 10,000 Swedish teenagers showed the combination of Asperger syndrome and mild mental retardation.