We study quantum transport properties of narrow GaAsAlxGa1-xAs wires and rings made by electron beam lithography. At low temperatures, clear signatures of Ah́aronov-Bohm quantum interference effects are observed due to the application of a perpendicular magnetic field. The ring devices show large amplitude (-5%) resistance oscillations periodic in magnetic flux penetrating the ring, which diminish in amplitude above -3kG. The wire devices show aperiodic resistance fluctuations as large as 100%, which persist into the quantum Hall regime. The large amplitudes observed result from the small number of transverse channels occupied below the Fermi level. © 1988.