In the paper entitled "Cellular Mechanisms for the Transfer of Calcium into and out of the Skeleton," which appears in the supplement to Pediatrics, Volume 47, No. 1, Part 2, page 211, January 1971, the photomicrographs for Figures 18 and 19, on pages 226 and 227, have been reversed. The legend for Figure 18 should appear with Figure 19 and vice versa.