1. Methods of aspirating tibial bone marrow from living laboratory animals (rabbit, guinea pig, mouse, and chicken) have been described. No method of aspirating marrow from living mice has been encountered in the literature.
2. The method would probably prove useful in obtaining marrow from the tibia of any small laboratory animal which has a flattened triangular area on the superior medial surface of the tibia.
3. In larger animals (rabbit and chicken), large amounts of marrow can be aspirated. Both smears and sections can be made.
4. The present method, if used in combination with the similar method of aspirating marrow from the ilium, will afford four different sites of aspiration. This should make possible the study of progressive changes in the marrow.