This research contributes to understandings of the occurrence of and associations between skeletal evidence of vitamin D deficiency and chronic respiratory infections across the life course based on human skeletal material from the Roman period sites of Isola Sacra in Italy (1st - 3rd centuries AD) and Ancaster in the United Kingdom (3rd - 4th centuries AD). Modern clinical data demonstrate a positive association between these two conditions that affects the ways in which they are experienced today, and may extend into the past. Macroscopic, radiographic, and histological evidence for skeletal manifestations of vitamin D deficiency and chronic respiratory infections were considered in the context of archaeological and historical evidence available for the Roman period in order to elucidate patterns in disease occurrence that reflect the unique local biologies of these two assemblages. Differing prevalence values for active and healed lesions caused by both conditions, as well as variation in age at death distributions and the relationship of lesions associated with vitamin D deficiency and chronic respiratory infections with one another and with age at death, provide information on the experience of both conditions and the potential interactions between them. Skeletal lesions caused by both conditions are present in individuals throughout the life course at Ancaster and Isola Sacra, with particular implications for disease experiences during infancy, adolescence, and pregnancy in the Roman period. These results point to a picture of morbidity and mortality at Ancaster that involves longer term survival of and more efficient immune responses to chronic disease processes, with higher levels of skeletal lesions indicating the presence of more "survivors" at this site. The combination of lower frequencies of skeletal lesions and higher mortality at Isola Sacra, on the other hand, suggests that fewer individuals may have survived to the point where they were able to mount a skeletal response to disease. / Dissertation / Doctor of Philosophy (PhD)