In most tissues, cell division is coordinated with increases in mass (i.e., growth). To understand this coordination, we altered rates of division in cell clones or compartments of the Drosophila wing and measured the effects on growth. Constitutive overproduction of the transcriptional regulator dE2F increased expression of the S- and M-phase initiators Cyclin E and String (Cdc25), thereby accelerating cell proliferation. Loss of dE2F or overproduction of its corepressor, RBF, retarded cell proliferation. These manipulations altered cell numbers over a 4- to 5-fold range but had little effect on clone or compartment sizes. Instead, changes in cell division rates were offset by changes in cell size. We infer that dE2F and RBF function specifically in cell cycle control, and that cell cycle acceleration is insufficient to stimulate growth. Variations in dE2F activity could be used to coordinate cell division with growth.