Porphyrias are the result of inherited enzymatic defects of the heme's biosynthesis chain. A porphyria crisis with abdominal pain and neurological or psychiatric signs may be precipitated by drugs. Our purpose is to list the main drugs which may precipitate phorphyria crisis, specifying which are contraindicated such as cefalosporins, anaesthetics, anti epileptic and anti tubercular drugs, and which are doubtful because of conflicting results published in literature. In any case it is necessary to verify any prescription before giving a drug to a patient with porphyria.