 Male and nonpregnant-female smokers 18 to 55 years of age, from the following subject groups: 1 patients with a DSM IV diagnosis of schizophrenia 2 patients with dual DSM IV diagnoses of schizophrenia and heroin andor cocaine dependence or abuse, or on methadone or beprenorphine maintenance and 3 healthy individuals with no family history of psychotic illness. 