Cerebrospinal fluid (CSF) dopamine levels were studied in 16 male patients who also were tested for self-reported extraversion using the Eysenck Personality Inventory. Log CSF dopamine was significantly correlated with extraversion as predicted by recent theoretical work integrating mesolimbic dopamine function and active responding to external incentives as psychobiological traits. CSF dopamine levels were uncorrelated with the total score on the Hamilton Rating Scale for Depression, self-reported neuroticism, and age. The results are discussed in relation to other biological models of extraversion such as the construct of sensation-seeking behavior.