OBJECTIVE The incidence of Asperger's syndrome is reported as above average in young people presenting with gender dysphoria. Patients with Asperger's syndrome, however, are prone to obsessive preoccupations. This paper points out that the apparent dysphoria may in some cases prove to be a transient obsession. METHODS Cases from the author's clinical practice were reviewed. RESULTS Two young men with histories suggesting Asperger's syndrome presented with strong convictions of gender dysphoria, asking for hormonal and surgical treatment. Treatment was withheld and after several years both came to repudiate their 'transgender phase'. CONCLUSIONS Patients asking for sex reassignment should be assessed for indications of Asperger's syndrome. Irreversible treatments should be withheld until it is clear there is a genuine issue of transsexualism.