People who do not identify with their biological sex are a small proportion of the population, but the issues they pose for law, medicine and society are significant. Trans people say they experience widespread discrimination in employment, housing and other areas. Eight states and more than 80 local governments have passed laws prohibiting discrimination based on gender identity, and transgender advocacy groups want Congress to follow suit. Many government and private employers already have “trans-inclusive” non-discrimination policies and help transgender workers fit in comfortably with colleagues and customers. Meanwhile, transgender advocates are urging health-insurance companies to cover the cost of sex-change procedures and calling on psychiatrists to delete or change the designation of “gender identity disorder” as a mental illness. But social conservatives oppose laws to bar gender discrimination and say transgender people are mentally ill and need therapy to help them accept their biological sex.