The mortality rates for London parishes which have been presented so far refer to the background level of mortality and do not include the effect of the plague epidemics. There were very serious plague crises in 1563, 1593, 1603, 1625 and 1665, and a lesser outbreak in 1636. There were relatively few plague deaths outside these years, but in the worst crises the annual death rate was well over 200 per thousand. In this chapter it will be argued that it is easy to misunderstand the effect of plague. The continuous supply of migrants from the countryside meant that even when the crisis mortality rate was so high, the population was replenished very rapidly after the end of the outbreaks. Outside these plague years, the great majority of deaths in London may be attributed to other diseases, and the disappearance of plague did not necessarily lead to a significant narrowing of the gap between deaths and births. The crises themselves, however, were very serious for their duration, and, as with mortality in general, their impact was unequally distributed between the different areas of the city.

Despite the social dislocation caused by its occurrence, plague was a relatively infrequent epidemic disease, although it was also endemic for much of the period in some of the poorer parts of the city. As T. McKeown has recently written: