Abstract. We prove existence and uniqueness of entropy solutions for the Cauchy problem for the quasilinear parabolic equation u t = div a(u, Du), where a(z, ξ ) = ∇ ξ f (z, ξ ), and f is a convex function of ξ with linear growth as ξ → ∞, satisfying other additional assumptions. In particular, this class includes a relativistic heat equation and a flux limited diffusion equation used in the theory of radiation hydrodynamics.