Only rudimentary progress has been made toward a practical theory of instabilities and their effects in small fusion targets. This is partly because a practical theory must combine several complicated physical phenomena. Most analytic studies of small amplitude Rayleigh- Taylor instabilities have neglected rotational flow, and the transition to large amplitude (nonlinear) behavior is probably dependent on poorly known fluid properties. Also, heat transfer and conduction may provide stabilization under some circumstances, while shear flow leads to Helmholtz instability, and ultimately some degree of pusher fragmentation must occur. Several mechanisms may couple the instabilities to the deuterium-tritium (D-T). The chief concern is added energy loss from the D-T volume and may result from increased area of a distorted interface, the enhanced emission from the D-T due to impurities introduced by the instabilities, and energy deposition by the D-T alphas in the pusher material rather than in the D-T.