A numerical solution in two dimensions of thermal effects in steady-state sliding confirms Blok's original analysis. It is shown that for transient sliding (assuming sudden contact), surface temperatures of about 50 percent of the steady-state value are reached in one sliding width of a contact patch and 80 percent in ten widths. If voids or singularities exist close to the surface in the moving body, transient surface temperatures easily exceeding the Blok steady-state value can occur.