Abstract: A segmented cylindrical reinforced plastic manhole structure comprising a cylindrical body surmounted by a transition element. The transition element is adapted to support a conventional manhole cover and frame assembly and has an opening closable by the manhole cover. The manhole structure body comprises a plurality of curved, nestable segments of cast or molded reinforced plastic material. Each segment is provided with vertical side edges configured to provide an interlocking joint between it and an adjacent segment and the segments may be so sized as to require two, three or more segments to complete the circumference of the manhole structure body. Each segment is provided with horizontal top and bottom edges configured to provide an interlocking joint between it and an adjacent segment thereabove or therebelow so that the segments may be arranged in tiers to provide a manhole structure body of desired height.