The theory of membrane tectonics proposed by Turcotte and Oxburgh [1973> to explain intraplate tensional features and earthquakes, and developed by Turcotte [1974> for an elastic lithospheric membrane, is extended to the case of a viscoelastic lithosphere. Such an extension may be expected to seriously modify the theory since, for all lithospheric viscosities except the very highest, the time scale for viscous relaxation is comparable to the time scale for changes in plate curvature. It is found that for most viscosities considered, the membrane stresses generated by changes in plate curvature do not exceed ~102 bars. We conclude that either the effective viscosity of the lithosphere is much higher than indicated by most studies, or membrane tectonic stresses play a secondary role in the generation of intraplate features and earthquakes.