Abstract.A rotationally symmetric n-dimensional surface in R n+1 , of enclosed volume V and with boundary in two parallel planes, is evolving under volume-preserving mean curvature flow. For large volume V , we obtain gradient and curvature estimates, leading to long-time existence of the flow, and convergence to a constant mean curvature surface.Mathematics Subject Classification (1991). 35K22, 58G11, 53C21.