The potential productivity of forests is an important parameter in the evaluation of vegetation as a carbon sink. At the same time, potential productivity can be considered as an indicator of growth conditions and also as a measure of available fuel loads, which, in Mediterranean-type ecosystems, are a main factor of regional fire incidence. The present work deals with the relationship between an estimation of forest potential productivity and the fire incidence registered in peninsular Spain. Fire incidence was characterized by means of several fire regime variables. In order to contrast the patterns obtained, a similar analysis of the relationship between fire regime and human population density was also carried out. The results show that higher fire incidence was registered in more productive areas. Potential productivity was correlated to variables related to the number of fires and to the area burned, whereas the population density was also correlated to the number of fire variables and to the area burned, but with lower correlation coefficients. Although it is difficult to establish cause-and-effect relationships between complex phenomena that depend on a large number of factors, finding statistically significant relationships between fire incidence and the estimation of potential forest productivity used over a long time period is considered very relevant. These relationships make it necessary to take into account the fire regime when evaluating both forests and other terrestrial ecosystems as carbon sinks so as to meet the demands of the Kyoto Protocol.