In this report we describe a simple and rapid staining technique for cartilage and bone embedded in Araldite. Semitbin sections of embryonic vertebrae obtained from 15 to 17 day mouse fetuses were stained using an aqueous solution 0.25% with respect to methylene blue, 0.25% with respect to azure A, and 0.5% with respect to Na2CO3, then counterstained with 1% aqueous pararosaniline chloride (MAP). Results were compared with toluidine blue stained sections. MAP permitted good discrimination of developmental stages of both cells and extracellular matrix within vertebral ossification centers during endochondral ossification. The technique is simple, rapid and applicable to plastic embedded sections, and can be used prior to ultrastructural examination.