PURPOSE: To classify types of vertebral hypoplasia and to investigate the prevalence and patterns of associated disc degeneration. MATERIALS AND METHODS: Defining vertebral hypoplasia as occurring when the AP diameter of a lower vertebral body is smaller than that of an upper ones, we retrospectively reviewed the MR images obtained in 34 cases of this condition invloving young adults. Two major types and two subtypes, a total of four different entities were classified as follows; type I: hypoplasia involving a single vertebral body; type II: hypoplasia in-volving serial lower segmental vertebral bodies; subtype a: hypoplastic body located anteriorly along the anterior spinal line; subtype b: hypoplastic body located posteriorly along the posterior spinal line. We also investigated each type of vertebral hypopla-sia and patterns of associated disc changes. RESULTS: Three different types were observed. In type IIa(n= 29), posterior disc occurred in 8/29 cases, diffuse degeneration in 21/29 patients, and posterior disc herniation in all. All type Ia cases(3/3) showed diffuse disc degeneration at both upper and lower disc levels, with posterior disc herniation, while both type IIb cases(2/2) showed diffuse disc degeneration, with bidirectional disc herniation. CONCLUSION: By identifying the exact patterns of vertebral hypoplasia, we were able to predict which portion of the disc was likely to degenerate.