Stable boiling in a rotating cylindrical annulus with continuous through-flow of water was obtained at heat fluxes as high as 818 000 Btu/(hr)(ft^2) (2. 58 MW/m^2) at atmospheric pressure. Incipient- and nucleate -boiling heat -transfer coefficients were obtained at accelerations up to 400 g's. Measurements were made of void fractions, radial temperature profiles, and wall pressures in the boiling fluid. Convective secondary-flow cells and fluid temperature inversions were revealed. Increased fluid thicknesses increased heat-transfer coefficients, but inlet liquid subcooling had no effect. Coefficients increased with acceleration at low heat fluxes, but at high fluxes varied less than the usual data scatter.