Temperature, a key climate change indicator, is expected to increase substantially in the Northern Hemisphere, with potentially grave implications for human health. This study is the first to investigate the association between the daily 3-hour maximum apparent temperature (Tapp(max)), and respiratory, cardiovascular and cerebrovascular mortality in Copenhagen (1999-2006) using a case-crossover design. Susceptibility was investigated for age, sex, socio-economic status and place of death. For an inter-quartile range (7 degrees C) increase in Tapp(max), an inverse association was found with cardiovascular mortality (-7% 95% CI -13%; -1%) and none with respiratory and cerebrovascular mortality. In the cold period all associations were inverse, although insignificant.