We study the blow-up set of a solution u(x, t) to the porous medium equation, u t = Δ(u m ), in Ω × (0, T) for two different boundary conditions, u(x, t) = f(x)/(T - t) or (x, t) = g(x)/(T - t) on ӘΩ × (0, T). Here m > 1 and Ω is a bounded smooth domain in ℝ N . We establish point-wise and integral conditions on f and g respectively in order to obtain regional or global blow-up.