Prolapsed tissue and removed interspace contents were obtained during hemilaminectomy for disc prolapse. The ultrastructure of the tissue was studied. Division of the material into annulus fibrosus and nucleus pulposus proved to be inaccurate. Chondrocytes were always the predominant cell type and could be classified into normal, cloning and necrotized types. Matrix vesicles were found in relation to the haloes of chondrocytes and seemed to be products of disintegrated chondrocytes. Findings of crystals in the vesicles were rare. The intercellular substance showed degraded collagen fibrils, which could be seen in spindle shaped cells as well. A dense amorphous material interpersed with collagen fibrils seemed to be a glycoprotein. A few elastic fibres were found, but without any evidence of severe degeneration. These findings represent changes occuring in cells and in the intercellular substance.