This study was motivated, in part, by the wellknown presence of fibrocartilage in regions of tendon that wrap around bone. These regions experience compressive as well as tensile stresses. We investigated the influence of cyclic hydrostatic pressure on the induction of fibrocartilaginous metaplasia in a non-cartilaginous cell source. Eight Achilles tendons were harvested from Wistar male rats and digested in collagenase solution to recover the cells, which were seeded into standard polystyrene flasks for pellet culture. Hydrostatic compression was employed as a mechanical stimulus to induce the changes in gene expression indicated by alteration of the phenotype of tendon to fibrocartilage. RT-PCR was carried out using GAPDH as a housekeeping gene. The results demonstrates that loading for 2 h caused initial 50% and 65% increases in the mean expression of aggrecan and type II collagen, respectively. This upregulation persisted for 24 h, by which time mean aggrecan and type II collagen expression were increased approximately 2 and 3-fold, respectively, relative to non-loaded controls. Expression of type I collagen in loaded samples was initially suppressed by 46% but had rebounded to 3-fold that of controls by 24 h. Expression trends in the long-duration experiment paralleled the initial response to 2 h loading, but differences were not statistically significant. Transmission electron micrographs from long-duration experiment reveal no obvious apparent differences in nuclei and cell organelles of each loaded and control tenocyte. Taken together, rat tendon fibroblasts subjected to cyclic hydrostatic compression displayed transient changes in gene expression associated with development of cartilaginous matrix, including increases in aggrecan and collagen type II mRNA and a suppression of collagen type I mRNA. Interestingly, collagen type II and aggrecan mRNA expression remained elevated 24 h later, while collagen type I expression had rebounded to exceed that of controls. Tenocytes pressurized for 7 days exhibited stable changes in gene expression that paralleled the initial transient change, suggesting possible transdifferentiation to a more cartilaginous phenotype.