The development of rust epidemics in tropical conditions of Brazil has been different than previously expected. Despite of high humidity the development is reduced to a minimum during the summer. High temperature was assumed to have a detrimental effect on the rust development. This paper reports the results of a study concerning the effect of high temperature on Hemileia vastatrix development. Temperature treatment of inoculated young plants at 40(0)C for 4 hours in 4 consecutive days was sufficient to prevent rust development. The curative effect was permanent indicating that the fungus was destroyed inside the plant tissue. Practical implications of such results are considered.