A computer model based on available materials property data has been developed to predict the lifetimes of first wall structural materials under a variety of reactor conditions. The model combines the materials property data with the appropriate ranges of limiting criteria to establish design lifetimes as functions of such relevant parameters as temperature and integrated neutron wall loading. Empirical equations developed from existing literature data were used to interpolate and extrapolate the required materials properties over the desired ranges. The present effort has concentrated on the evaluation of two candidate structural materials, namely, Type 316 stainless steel and a vanadium-base alloy (V-15% Cr-5% Ti). Curves have been derived that show the estimated lifetime and life-limiting property as a function of temperature for a specified set of design criteria, e.g., maximum swelling of 4%, minimum uniform elongation of 1%, and total creep strain of <1%, for an applied stress of 103 MPa (15 ksi). The results obtained indicate a much longer design lifetime for the vanadium-base alloy than for stainless steel under the conditions of interest. The computational model has been incorporated into the Tokamak Power Plant Systems Program at Argonne National Laboratory.