In this paper an attempt is made to describe the pattern of declining mortality in British Guiana between 1911 and 1960. Specifically we identify the disease-specific mortality rates whose declines contributed most to the overall improvement, we consider the possibility that changing economic circumstances may have contributed to the decline in mortality, and we survey the improvements in public health facilities which occurred during the period. Broadly our conclusion is that improvements in public health facilities and not economic advances were responsible for the dramatic decline in mortality which was experienced. Before 1940 these advances took the form of improvements in the quality of the country’s water supplies, in methods of disposing of waste, and in medical facilities especially on the colony’s sugar estates. In addition, there was an advance in the dissemination of information with respect to pre- and post-natal care. In the postwar period British Guiana’s famous D.D.T. experiment was the most important reason death rates continued to fall.