In this note, the use of homogeneous polynomial Lyapunov functions (HPLFs) for robust stability analysis of linear systems subject to time-varying parametric uncertainty, affecting rationally the state space matrix, is investigated. Sufficient conditions based on linear matrix inequalities feasibility tests are derived for the existence of HPLFs, which ensure robust stability when the uncertain parameter vector is restricted to lie in a convex polytope. It is shown that HPLFs lead to results which are less conservative than those obtainable via quadratic Lyapunov functions.