To evaluate and assess families, two problems arise first different conceptualizations, and second, different assessment devices. It means these is yet to reach to a generally agreed assessment tool (keitner, et al; 1996). Hence standardization and validation of such devices would be substantial for the field. Aim: standardization of Family Assessment Device (FAD), using reliability coefficient with internal consistency, Z values, and percentile rank indices. FAD includes 60 items on family functioning, with six subscales including problem solving, communication, roles, affective involvement, and affective responsibility.Subjects are mothers (N=494) of primary school children in Tehran who were selected through stratified random sampling. Test retest reliability was evaluated in a 2 - weeks intervals.The reliability was calculated using kronbach Alpha in each subsca1e.The results revealed a high Alpha value in all dimensions. Also Z values of each dimension are demonstrated.