The discovery of tetracycline, an autofluorescent antibiotic that fixes to sites of active mineralization has enabled histologic study to pass from static to dynamic bone analysis. Two cycles of oral tetracycline, separated by a period of 12-14 days, provides an intermittent marker for the study of bone cynetics. Any tetracycline administered within therapeutic ranges will label the bone. Characteristics of the deposit and the time lapse between the doses administered provide information about the degree of advance of the mineralization process.