1. A method is described for the supravital staining of articular cartilage.
2. The full thickness of articular cartilage of the distal portion of the femur of the rabbit is stained about ten to fifteen minutes after the intra-articular injection of three to four cubic centimeters of 0.5 per cent solution of neutral red.
3. Two cationic dyes (toluidine blue and methylene blue) and neutral red diffused readily through articular cartilage. Two anionic dyes did not.
4. Local injections of dye into the medullary space of the epiphysis failed to stain the overlying articular cartilage. Perfusion of dye through the aorta failed to stain articular cartilage which was isolated from the synovial membrane.
5. Diffusion of dyes into articular cartilage ceased one hour after death.