The possible links between personality psychology and psychopathology are examined with the goal of understanding the constraints that set boundaries to the possible contributions of one to the other. The reciprocal nature of these contributions is described. The historical survey looks at the early concepts of the humors and temperament, at the concept of a general vulnerability to psychosis and deviance--represented by the 19th-century concept of degeneracy--and at later typologies arising from the work of Eysenck, Freud, Kretschmer, Pavlov, and Sheldon. The impact of current developments in neuropsychology and in cognitive psychology is discussed.