1. Chronic tuberculous osseous lesions were induced consistently in eight- to ten-week-old unvaccinated guinea-pigs by the insertion of Gelfoam impregnated with mycobacterium tuberculosis into the metaphysial region through a drill hole in the distal part of the femur. Typical tuberculous lesions developed by three weeks and many of them were followed for twelve weeks or more.

2. This experimental model establishes a reliable method of producing a localised lesion at a predetermined site without early death of the animal. The model is sufficiently similar to the human lesion, and may offer a reliable system for further investigations.

3. It was observed that streptomycin penetrates readily into tuberculous osseous lesions. The concentration of streptomycin found in the tuberculous lesion after a single intramuscular injection was much higher than the concentration considered sufficient to have an inhibitory effect on the human type of mycobacterium tuberculosis.