STUDY DESIGN: In vitro motility assays were carried out using rat intervertebral discs (IVDs). OBJECTIVES: To demonstrate the motile properties of the cartilage endplate (CE) chondrocytes and the effect of notochordal cells on this property. LITERATURE REVIEW: Although previous in vivo studies have provided evidence for the migration of CE chondrocyte from hyaline CEs into the notochordal nucleus pulposus (NP), it is unclear if CE chondrocytes of the IVD actually have motile properties. In addition, the effect of notochordal cells on these properties has not been reported. MATERIALS AND METHODS: Notochordal cells and CE chondrocytes were harvested from three-month-old male Wistar rats and cultured separately. The motility was assayed in quadruplicate using a 48-well microchemotaxis chamber and a gelatin-coated 8-micrometer polycarbonate membrane filter. The control medium (serum-free culture medium), notochordal cells (4x, 2x, 1x and 0.5x10(6)) and concentrated conditioned medium (10-, 50-fold) where notochordal cells were cultured were loaded into the wells of the lower chamber, and CE chondrocytes were added to the wells of the upper chamber. At the end of the assays, the CE chondrocytes that migrated to the bottom side of the membrane filter were stained, counted, and compared. RESULTS: Compared with the control medium, the notochordal cells (N = 4x, 2x, 1x and 0.5x10(6)) and concentrated conditioned medium (10- and 50-fold) significantly increased the chemotactic motility of the CE chondrocytes in a number- and concentration-dependent manner (p<0.05). CONCLUSION: The CE chondrocytes of the intervertebral disc are motile, and soluble factors produced by notochordal cells induce the chemotaxis of CE chondrocytes.