BACKGROUND Sexual behaviour is often altered in chronic illness. OBJECTIVE To evaluate sexual behaviour in coeliac patients before and after treatment with a gluten-free diet. METHODS Fifty-five adults with coeliac disease and 51 age- and sex-matched healthy controls. METHODS Routine clinical and laboratory work-up was used for diagnosis of coeliac disease. Age of first sexual intercourse, prevalence of individuals who were sexually active, frequency of intercourse, reduction in sexual desire, difficulty in attaining orgasm, pain during intercourse, and prevalence of individuals defining themselves as satisfied with their sexual life were investigated by an anonymous, self-administered questionnaire administered before and after one year's treatment with a gluten-free diet in coeliac patients, and only once in controls. Analyses included clinical conditions, demographic and socio-economic data. RESULTS Compared with controls, untreated coeliac patients had a significantly lower frequency of intercourse and a lower prevalence of individuals satisfied with their sexual life. Patients with overt and subclinical coeliac disease did not show significant differences for any indices of sexual behaviour. Compared with untreated conditions, coeliac patients after one year of treatment had improved values for all indices of sexual behaviour: differences were significant for frequency of intercourse and prevalence of individuals satisfied with their sexual life. CONCLUSIONS Untreated coeliac disease, even in its subclinical presentation, is associated with disorders in sexual behaviour which are improved by the dietary treatment.