The advent of the utilization of the T-tail in light aircraft design requires that new consideration be given as to the effect of imposed loads on the empennage and on the stability derivatives, each of which is greatly influenced. This thesis presents the results of wind tunnel tests of a model consisting of a fuselage, a vertical fin, and a horizontal stabilizer. Five different horizontal stabilizers (T-tails), each with a different aspect ratio and longitudinal position were tested. Theoretical calculations are compared with the test results, and discussion given as to the optimization of these geometric parameters.