Biological factors involved in the lack of control associated with impulsive behavior have been investigated. We have performed lumbar punctures and the glucose tolerance test (GTT) in a consecutive series of 18 pathologic gamblers. Concentrations of 5-hydroxyindoleacetic acid (5-HIAA), the metabolite of the monoamine neurotransmitter serotonin, have been measured in the cerebrospinal fluid (CSF). Other CSF monoamine metabolites and peptides have also been measured. Plasma levels of insulin and glucagon during the GTT will be quantified. Personality variables have been measured using three personality questionnaires. We will compare the pathologic gamblers with normal controls and alcoholics and correlate the biological factors claimed to be involved in impulse dyscontrol with the personality variables.