Feed supplements are commonly used to treat and prevent articular disorders. The aim of this study was to investigate the effect of glucosamine/chondroïtin sulphate (G/CS) and hydroxyapatite (HxAp) on equine chondrocyte growth in vitro. Equine chondrocytes were collected from articular cartilage of the metacarpo-phalangeal joint from 4 horses and were submitted to enzymatic digestion. Chondrocytes were cultured during 7 days in 6 wells plates. Cell medium was either used without or with 5 dose regimens of G/CS and HxAp (10, 1, 0.1, 0.01 and 0.001 mg/ml). Chondrocyte proliferation was quantified by cell counts performed at day 3, 5 and 7. Each condition was performed in quadriplicate. In all chondrocyte cultures (control, G/CS or HxAp; 250.000 cell/well seeded at day 0) the global cell growth profile showed a decrease at day 3 and then an increase which stabilised at day 7. Results for cell counts showed a significant effect of G/CS and HxAp at day 3 and 5, HxAp being higher than G/CS (p<0.05) and both being higher than control (p<0.05) except G/CS at day 5. At day 7, no significant difference between control, G/SC and HxAP was observed. It appeared that the dosis of 10 mg/ml for G/CS and HxAp induced a reduction of cell growth; probably by a toxic effect on cells. No significant dose regimen effect was observed on cell counts except for HxAp at 1 mg/ml at day 5, which led to significantly higher cell counts (p<0.05). It can be concluded that the tested substances composed by glucosamine/chondroitin sulphate or hydroxyapatite could both stimulate equine chondrocyte growth in vitro. Further investigations including a larger number of animals and investigations regarding increase in biomass (e.g. protein concentration) will be interesting.