Pandemic events are surpassingly rare in human history. Yet the period we call late antiquity could be considered the age of pandemic disease. It began and ended with the Antonine plague that erupted in the mid-160s A.D. and the Justinianic plague of the mid-6th c. Modern interest in these pandemics has waxed and waned. It was long taken for granted that these events played a major rôle in the fate of the Roman empire. In the mid-20th c., however, attention subsided. Historical demography struggled to make inroads into the discipline of ancient history. In the case of the Antonine plague, a critical article of J. F. Gilliam turned focus away from the disease for a generation. Only in the last 20 years, with the rise of historical demography in ancient studies, and a broader interest in environmental history, have the Antonine and Justinianic plagues received their proper due. Attention has focused on the epidemiology and impact of these events. The Antonine plague is most plausibly identified as smallpox, based on the presentation of the disease described by the contemporary physician Galen, and should qualify as the first pandemic in all of human history. It struck the empire at the apex of its power and prosperity. Its severe demographic effects now seem widely accepted, although there is lively debate about its long-term geopolitical and social consequences. For the Justinianic plague neither its demographic scope nor the long-range consequences are in doubt. Securely identified by both clinical description and paleomolecular evidence, Yersinia pestis arrived in 541 and struck recurrently for over two centuries; like the Black Death in the 14th c., the first bubonic plague fundamentally reshaped the trajectory of European populations.