Abstract: This application disclosed a modular stairway system for circular structures or other structures having non-linear walls. The invention comprises a plurality of first stringer means, a plurality of first connecting means for joining the first stringers, a plurality of second stringer means horizontally spaced from and parallel to the first stringer means, and a plurality of adjustable second connecting means for adjustably joining the second stringers such that the first and second stringers conform to the curvature of the structure. A plurality of stairs are horizontally interposed between the first and second stringers, and a stair mounting means for securing the stairs to the first and second stringers are provided.