The study examined the unique relationships of Behavioral Inhibition System (BIS), Fight-Flight-Freeze System (FFFS) and Behavioral Approach System (BAS), and Sensitivity to Punishment (SP) and Sensitivity to Reward (SR) with social interaction anxiety and social observation anxiety. A total of 200 adults completed the Behavioral Inhibition System/Behavioral Activation System scales, the Sensitivity to Punishment and Sensitivity to Reward Questionnaire, and questionnaires measuring social interaction anxiety and social observation anxiety. Multiple regression analyses revealed that both forms of social anxiety were associated with SP, BIS-Anxiety and BIS-Fear, and negatively with BAS-FS. The theoretical implications of the findings for reinforcement sensitivity theory are discussed.