The current geographic range of malaria is much smaller than its potential range. In many regions there exists a phenomena characterized as "Anophelism without malaria." The vectors are present but malaria transmission does not occur. Vectorial capacity often has been used as a parameter to estimate the susceptibility of an area to malaria. Model computations with global climatological data show that a dynamic concept of vectorial capacity can be used as a comparative risk indicator to predict the current extent and distribution of malarious regions in the world. A sensitivity analysis done in 3 distinct geographic areas shows that the areas of largest change of epidemic potential caused by a temperature increase are those where mosquitoes already occur but where development of the parasite is limited by temperature. Computations with the model presented here predict, with different climate scenarios, an increased malaria risk in areas bordering malaria endemic regions and at higher altitudes within malarious regions under a temperature increase of 2-4 degrees C.