Direct measurements have been made of the effect of strain on the critical temperature of tin, aluminum, and indium films. The films (<1000 Å) were vacuum deposited onto glass and mylar substrates at room temperature and were then strained by mechanically bending the substrate in liquid helium.Tcdepended linearly on the strain over the range of observation, ∼10−3, for both tensile and compressive bending. The slopes of theTcvs strain curves were 8.7° and 9.1°K per unit strain, respectively for tin and aluminum films on glass substrates and 4.9° and 3.8°K per unit strain for tin and indium films on mylar substrates. Earlier measurements1,2have indicated considerable variation in theTcdependence on strain from film to film, but our data are quite reproducible and do not seem to depend markedly on the evaporation conditions. For an isotropic material or an anisotropic material for which the relative orientation of the strain axis and the axes of crystal symmetry are known it is possible to relate the change inTcto a corresponding volume change. On this basis one can compare the results on thin films with strain and pressure measurements on bulk samples. ComparingdlnTc/dlnVfor thin films and bulk samples3we find that the values for aluminum agree within five percent, those for tin films on glass are lower by thirty percent, and those for indium films are higher by a factor of three. The change inTcdue solely to a change in sample volume can be calculated as a function of the Debye temperature on the basis of the McMillan theory1by using the Gruneisen relation and taking &lgr;, the phonon‐mediated electron interaction, to be inversely proportional to the square of the Debye temperature. Comparing experimental results with these calculations we find that the experimental results fordTc/d&thgr;Dlie within the limits imposed by &mgr;* = 0.1 to 0.2 for bulk aluminum, tin, and indium and thin‐film aluminum and tin. (Materials for which the Coulomb pseudopotential, &mgr;*, has been measured lie within these limits.)