The decline of mortality in the more developed nations has been related to two major influences, economic development and the introduction of medical measures. The contribution of medical measures has been a source of continuing controversy. Most previous studies employed either a birth cohort or calendar year arrangement of mortality data to address this controversy. The present study applies an age-period-cohort model to mortality from respiratory TB in England & Wales, Italy, and New Zealand, in an attempt to separate economic influences from that of medical measures. The results of the analysis indicate that while the overall contribution of medical measures is small, when examined by calendar year, specific birth cohorts both in Italy and England and Wales benefited substantially from these measures. The environmental conditions in New Zealand, however, were such that the introduction of medical measures barely affected declining mortality levels from respiratory TB.