Daily myocardial infarct deaths from Brisbane, 29 degrees 28' S, and Montreal, 45 degrees 30' N, were used to derive a "pool of susceptible individuals". Pool size had no effect on the minimum death temperature but large pools increased the value of the acceleration temperature in Brisbane and the maximum death temperature in Montreal. Moderately sized pools in Montreal appeared to produce reduced death rates in cold conditions from both cold avoidance and habituation. A generalized relationship between temperature and myocardial infarct death is postulated.