Objective: Gender Identity Disorder is a rare condition in which individuals experience their gender identity as being incongruous with their phenotype. An important factor related with this disorder is family, which plays a role in etiology and maintenance of the disorder. Finding the relationship between family functioning and Gender Identity Disorder (GID), can be useful for enhancement of the interventions program, to help the patients and evaluation of this relationship is aim of this study.

Materials & Methods: This study was a cross – sectional and case-control research. In this study 37 individuals who have been reffered to Iran Forensic Medicine Organization with Gender Identity Disorder (GID) diagnosed by pschiatric commision filled demographic questionnaire and Family Assessment Device. Matching the control variable (sex, age, and education), 37 available individuals who have no psychiatric problem were selected in control group and filled the device. Data was analized using by T- test for independent groups.

Results: Results showed that "family functioning" (P=0.034) and some functional demensions including "Affective involvement" (P=0.03), "Control of behavior" (P=0.021) and "Affective responsibility" (P=0.009) in Gender Identity Disorder (GID) group in comparison with control group were more unsuficient. But there is no significant diffrence in "Roles" (P=0.15), "Problem Solving" (P=0.16) and "Communication" (P=0.066) between two groups.

Conclusion: In regard to findings of this study, programs through the family intervention can be useful for Gender Identity Disorder (GID) patients. In other hand by viewing these factors planing some programs for prevention and treatment of Gender Identity Disorder (GID) is suggested.