The motion of simultaneously rising and growing vapor bubblesin a uniformly superheated liquid is analyzed, and the predicted bubble velocities are shown to be in good agreement with available data. Using a quasisteady state approximation to describe the drag, and existing bubble growth theory to describe the growth rate, the equation of motion is solved for two ranges of bubble size encountered in nucleate boiling. For smaller bubbles (R<0.04 cm.) an analytical solution is obtained, and for larger bubbles (R>0.07 cm.) a numerical solution and analytical asymptotic solutions are obtained.