We consider the effect of weak nonmagnetic disorder on two chains of interacting fermions (with and without spins) coupled by interchain hopping. For the spinless case, interchain hopping increases localization for repulsive interactions but stabilizes the s-wave superconducting phase for attractive interactions. For the case with spin, the d-wave phase arising from purely repulsive interactions in the clean system is destroyed by an infinitesimal disorder, while for attractive interactions, the s-wave superconductivity is more resistant to disorder than in the one-chain case. In each case we compute the localization length and the conductivity.