Five cases are presented which seem to distinguish those who are habitual drug users through preference from the accidental type which fundamentally desires to be free from the drug and return to normal life associations. They uniformly confirm McDougall's hypothesis of the closer association of the alkaloid drugs with the temperament of the introvert. They suggest the connection of the morphine habit with neurotic tendency and to a less degree with submissiveness and with a lack of self-sufficiency. (PsycINFO Database Record (c) 2006 APA, all rights reserved)