Baroclinic instability is examined in a two-layer, quasi-geostrophic model for linearized mesoscale waves (i.e., with periods of a few months and length scales near the internal deformation radius). The mid-ocean wave environment includes the, β-effect, bottom topography and mean currents, all presumed to vary only on scales much greater than those of the wave. An optimization of the local rate of unstable growth shows the process to be potentially important for mesoscale generation: typically, a vertical velocity shear of 5 cm sec−1 permits an e-folding time of two months. The many processes included in the model allow a great variety of behavior; for example, although both β and topography are generally stabilizing by themselves, their combination can be destabilizing.