The dissipative behavior in thin films of YBa2Cu3O7- has been investigated under the influence of a temperature gradient. By using the sample configuration itself as a thermometer, a method has been developed for the study of flux dynamics in the presence of a temperature gradient. The temperature and magnetic-field dependence of the transport entropy was measured, and the influence of grain boundaries on this quantity was investigated. For an epitaxial YBa2Cu3O7- film near Tc, we obtain the value -dHc2/dT=20.5 T/K and the Ginzburg-Landau parameter GL=8010. © 1991 The American Physical Society.