The clinical response of growth plate to exogenous forces is well recognized, although the organ-level mechanisms are poorly understood. Physeal cartilage from 5- to 7-day-old bovine distal radii was subjected to 245 N of tension or 245 N of compression (0.012 MPa) in organ culture over a 24-h period. Eleven specimens (six tension, five compression) were assayed for cellular proliferation with tritiated thymidine. Eighteen specimens (12 tension, six compression) were assayed for synthetic activity with radioactive sulfate. Media were assayed for prostaglandin production. Tension increased whereas compression decreased synthetic activity and prostaglandin production by physeal cartilage in explant culture over a 24-h period. There was no significant change in thymidine uptake. Physeal cartilage can respond to both tension and compression and, in the short term, appears to alter synthetic activity without changing the rate of cell proliferation. This study system allows local sampling and manipulation of the physeal organ environment and may lead to ways of approaching growth-plate pathologies in vivo.