Since 1850, the CO (2) content of the atmosphere has increased from 280 to 360 ppm, and the average surface temperature has risen from 14.6 to 15.3 C . A further increase between 1.8 and 4.0 C is expected for the 21st century. Temperate and cold climate zones are affected predominantly, but tropical regions are not spared. At the same time, the world wide climate effects of the "El Niño Southern Oscillation" are amplified. Global warming enhances the growth of tropical pathogens (malarial plasmodia, leishmania, yellow fever virus, dengue virus, West Nile virus, Vibrio cholerae) and vectors (anopheles, aedes, culex, and phlebotomus mosquitos; hard ticks). Global warming may lead to the emergence of diseases which at present are not endemic in Germany, like West Nile fever, Dengue fever, or Leishmaniases, and to enhanced transmission of borreliosis and tick-borne encephalitis. Malaria and cholera, in contrast, are influenced more strongly by socioeconomic factors. Improved surveillance and intensified research on the relationship between climate change and infectious diseases is needed.