In this study a variety of procedures were utilized to examine the histochemical characteristics of cartilage, bone matrix, and osteoid in experimental low-phosphorus, low-calcium, and hypervitaminosis D rickets. The results obtained indicate that each of such tissues exhibits different histochemical properties and that these properties do not vary with the type of rickets induced. Therefore, the data acquired constitute additional evidence that osteoid differs from bone matrix. Interpretation of the observed reactions permits a deduction as to the nature of this difference.