The causes of the retardation of the infant mortality decline in the latter part of the nineteenth century in England has been the subject of debate amongst historians and medical professionals for the last hundred years. The varieties of explanations that have been offered tend to only indicate the overwhelming complexity ofthe question. This thesis examines the issues surrounding the infant mortality decline in the late nineteenth and early twentieth centuries in five English urban areas. It appears far more plausible to consider that the national figures only represent an average of a multitude of local circumstances and it is only by reference to these that a viable explanation for the infant mortality decline can be detected.