Abstract: This application discloses a modular stairway system for circular structures or other structures having non-linear walls. The invention comprises a plurality of first stringer means with a plurality of first connecting means integral to said first stringer means for joining the first stringers, a plurality of second stringer means horizontally spaced from and parallel to the first stringer means with a plurality of adjustable second connecting means integral to said second stringer 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.