Resonant tunneling transport was studied in GaAs‐AlGaAs single well, double barrier structures. Negative differential resistance at 77 and 300 K was observed in devices grown by metalorganic chemical vapor deposition. The observed peak to valley ratios were 6 to 1 and 1.48 to 1, respectively. The presence of GaAs spacer layers was found to have a distinct effect on the 300 K current versus voltage characteristics. Microwave oscillation at frequencies up to 3.0 GHz was observed at 300 K. A short discussion of the oscillation frequency limits of our structure is presented.