Gray (1987) proposed two systems underlying much of our behavior and personality. One system (Behavioral Inhibition System, BIS) relates to avoidance or withdrawal behavior, whereas the other system (Behavioral Approach System, BAS) relates to approach behavior. Underreactivity and overreactivity of those systems have been presumed to explain a broad range of psychopathologies. Despite the increasing interest and use of questionnaires measuring BIS and BAS reactivity in psychopathological research, studies examining psychometric qualities of these measures in clinical samples are scarce. This study evaluated the psychometric properties of the BIS/BAS Scales and the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ) in eating disordered patients. Structural validity is investigated by means of Confirmatory Factor Analysis. Convergent validity is examined by investigating associations with conceptually related personality traits. For the BIS/BAS Scales, CFA favors a five-factor structure in line with a recent revision of Gray’s theory (Gray & McNaughton, 2000). For the SPSRQ, sufficient support was found for a two-factor structure. Reliability and validity of both instruments are in line with previous reports.