Millimeterwave Gunn-oscillators have for the first time been fabricated using gallium arsenide grown by molecular beam epitaxy. Material produced by this new method of epitaxy has yielded c.w. integral heat sink oscillators with up to 20 mW of r.f. power at 90 GHz, 10 mW at 100 GHz, and 4 mW at 110 GHz. These results are comparable with those obtained from devices using gallium arsenide grown by other techniques such as vapor- or liquid-phase epitaxy.