The prevalence of the Rett syndrome was found to be approximately 1:15,000 in south-western Sweden. About 40 cases have now been traced in this country, the majority during the last 2 yrs. Experiences of over 20 yrs in efforts to obtain information on the etiology and pathogenesis are summarized. The neurobiological approach used in Gothenburg today to try to reveal the origin is described. A plea is made for developmental screening of deteriorating hand skill as a tool for early identification of potential cases of the Rett syndrome.