Three common subtypes of porphyria give rise to neuropsychiatric disorders; acute intermittent porphyria, variegate porphyria, and coproporphyria. The second two also give rise to cutaneous symptoms. Neurological or psychiatric symptoms occur in most acute attacks, and may mimic many other disorders. The diagnosis may be missed because it is not even considered or because of technical problems, such as sample collection and storage, and interpretation of results. A negative screening test does not exclude the diagnosis. Porphyria may be overrepresented in psychiatric populations, but the lack of control groups makes this uncertain. The management of patients with porphyria and psychiatric symptoms causes considerable problems. Three cases are described to illustrate some of these issues. Advances in molecular biology permit identification of patients and latent carriers in the family. Care to avoid relapses and improved treatments have reduced the mortality.