The purpose of this study was to determine the two-dimensional temperature field for a fluid in slug flow through tubes with uniform mass injection and linearly decreasing wall temperature. A series solution was obtained, the first ten eigenvalues for which were determined from the characteristic equation by the method of Runge-Kutta. Expressions for local conductive heat flux at the tube wall and local Nusselt number were obtained as a function of inlet Peclet number, injection Peclet number, tube radius, temperature boundary conditions, and fluid properties. Sample results are presented for several injection rates at different wall temperature conditions. In general, mass injection was found to decrease the local heat flux and increase temperature driving force causing a decrease in the Nusselt number.