A measure for assessing family involvement in traumatic brain injury rehabilitation (TBI) was developed. The Family Involvement Assessment Scale (FIAS) is theoretically based on Barrer's (1988) model of family involvement in TBI rehabilitation, which highlights two dimensions, “support” and “involvement.” An initial pool of 337 items believed to be related to the constructs of “support” and “involvement” was generated. Forty-nine items were systematically selected from the initial pool and included in a preliminary assessment form in which 172 professionals rated the items on the dimensions of support and involvement. Eleven items were subsequently eliminated from the original pool based on these ratings. The remaining 38 items were used by 181 of the professionals to evaluate the involvement of actual family members of patients receiving TBI rehabilitation services in their programs. A factor analysis was performed on a remaining pool of 38 items. Three factors with an eigenvalue greater than 2.0 accounted for 48.8% of the total variance. One item that did not significantly load on any of the factors was eliminated. The FIAS includes a final set of 37 items, comprised of three subscales based on the factor analysis. Two of the scales, the Involvement-Rehabilitation (IR) scale and the Support (S) scale correspond, respectively, to Barrer's (1988) dimensions of “involvement” and “support.” The third scale, Involvement-Patient (IP), is a unique construct that measures the degree to which a family member is involved in the rehabilitation process with respect to their involvement and relationship with the patient. The three scales yielded adequate internal reliabilities. Correlation coefficients between the scales indicated that the IR and S scale are not statistically related, but the IP scale is significantly related to both the IR and S scales. Interrater and test-retest reliability, and concurrent and predictive validity for the FIAS are still to be determined. © 1997 National Academy of Neuropsychology. Published by Elsevier Science Ltd