We present results for the effect of diagonal disorder on the conductance of molecular wires, using a simple one-dimensional tight-binding picture. We show that diagonal disorder affects three aspects of the conductance : (i) It produces large conductance fluctuations from wire to wire. (ii) It reduces the conductance in situations where the transfer would be resonant, and enhances the conductance when transfer is nonresonant. (iii) It gives near-exponential conductance decays with wire length.