In this paper the authors study a model validation problem pertaining to linear fractional uncertainty models. They extend the previous validation approaches, based upon either time or frequency measurements, to one using simultaneously time- and frequency-domain data. They show that this problem can be reduced to two independent convex feasibility tests, each of which corresponds to the time- or frequency-domain data alone, and each can be verified numerically using available algorithms and software programs. The merit of such a mixed time-and frequency-domain approach, therefore, lies in that not only can it accommodate the two distinctively different types of measurement data simultaneously, but also from a computational standpoint it will not suffer from a complexity growth beyond that associated with the existing time-domain tests.