Background The Cloward anterior interbody fusion is commonly performed for cervical disc herniation or spondylosis. In followup studies, various authors have noted clinically relevant adjacent-level degeneration. However, factors associated with adjacent-level degeneration are not well known. Questions/purposes We asked whether the postoperative sagittal segmental alignment of the fused vertebrae could be used as a predictor of adjacent-level degeneration. Methods We retrospectively studied 107 patients, aged 35 to 55 years, with one-level cervical disc disease between C4 and C7 operated on from 1985 to 1995 by discectomy and one-level anterior cervical fusion according to the Cloward procedure. In standard radiographs of the cervical spine in lateral view, the alignment of the involved intervertebral space (sagittal segmental alignment) and the sagittal alignment of the cervical spine were measured and the adjacent-level degeneration was assessed using the Kellgren and Lawrence criteria. The minimum followup was 10 years (mean, 16 years; range, 10-23 years).