Consanguineous marriage customary in many societies. Causes increased birth prevalence of infants with severe recessive disorders. Medical proposals to discourage it exist. Experts reject discouragement as unethical in genetic counselling. Ignores social importance of consanguineous marriage. Discouragement proves ineffective. Custom enables better genetic counselling. Recommend identifying high-risk families. Provide them risk information. Offer carrier testing when feasible.