The Plains Cree, Assiniboine and Ojibwa of the Brandon House area were afflicted by the 1819-20 measles epidemic. Each group experienced different mortality rates as a result of differences in their coping strategies. This study examines the various mortality rates through factors such as nutritional intake, suitable housing and overall health. It then attempts to apply the Human Behaviour Model, as developed by Michael Trimble, to the situation at Brandon House and look for anomalies in his model. Finally, this thesis seeks to take a holistic approach in understanding the interrelationship between the local and global events occurring in the early part of the 1800s, as well as the political, social and economic changes experienced by the First Nations peoples. At this time, these people experienced sociocultural and economic changes that both impacted and were impacted by the 1819-20 measles epidemic. In examining the diffusion of the 1819-20 measles epidemic, Michael Trimble's model is based upon the Mandan-Hidatsa horticultural community. While some aspects of his model are applicable to the hunting-based economy of the First Nations people at Brandon House, socioeconomic factors including alcohol consumption are neglected. In addition, a more in-depth analysis of nutritional intake (diet) and social and mental health illuminate the importance of these factors on the immune system and their impact on mortality rates. As nutritional deficiency increases and health decreases, the immune system becomes compromised and a person becomes more susceptible to disease and secondary infections. As the Plains Cree and Assiniboine experienced a decline in their role as middlemen in the fur trade, they began to lose their economic and political position with the Mandan First Nations. Within the historical fur trade literature, political and socioeconomic events such as the "Horse Wars" appear to be removed from the affects of the disease, this is not always the case. Thus, the consequences of the 1819-20 measles epidemic were influenced by human behaviour since the cultural responses to disease are as important as the epidemiological factors.