A reaction-diffusion equation with power nonlinearity formulated either on the halfline or on the finite interval with nonzero boundary conditions is shown to be locally well-posed in the sense of Hadamard for data in Sobolev spaces. The result is established via a contraction mapping argument, taking advantage of a novel approach that utilizes the formula produced by the unified transform method of Fokas for the forced linear heat equation to obtain linear estimates analogous to those previously derived for the nonlinear Schrödinger, Korteweg-de Vries and "good" Boussinesq equations. Thus, the present work extends the recently introduced "unified transform method approach to well-posedness" from dispersive equations to diffusive ones. -boundary value problems, wellposedness in Sobolev spaces on the half-line and the finite interval, L 2 -boundedness of Laplace transform, unified transform method of Fokas. F. Weissler, Local existence and nonexistence for semilinear parabolic equations in L p . Indiana Univ. Math.