Background and Objectives: This study aimed to compare Gary Behavioral Systems (behavioral activation system and behavioral inhibition system) in normal couples and those engaged in marital infidelity.

Material and Methods: The research was descriptive and causal-comparative. Study population consisted of normal couples and couples who were betrayed in the cities of Tehran, Karaj and Tabriz that were referred to counseling clinics. Study sample consisted of 100 clients; 50 normal couples and 50 couples who were involved in marital infidelity. Sampling was targeted. To collect data, Grey-Wilson's and wife infidelity questionnaires were used.

Results: Inhibition of behavior in normal couples was higher than couples involved in marital infidelity which was significant at P <0.01. The behavioral activator system in couples involved in marital infidelity was higher than normal couples and this difference was significant at P <0.01 level.

Conclusion: Couples who have activation system of high sensitivity are more involved in the phenomenon of marital infidelity compared to the couples who are at high behavioral inhibition system.