Recurrent selection for resistance to Sclerotinia head rot was carried out for 15 cycles on a restorer sunflower population created in 1978. For the first 3 cycles a test measuring rate of extension of mycelium on the back of capitula was used; from the fourth cycle onwards, it was combined with a test based on ascospore infections, which repeat more closely natural infections. An 80% reduction in diseased area was obtained in 4 cycles, with the first test, thereafter the population remained stable and homogeneous for this character. In 12 cycles the latency index (measure of incubation period) of the ascospore test doubled, and the best relation with cycle was a simple regression, with a significant slope, indicating that further improvements should be possible. The hybrids made with the first, sixth and fifteenth generations of the population showed a halving of percentage attack in the field and hybrids with some of the best lines bred from several cycles presented even greater levels of resistance. This population is available to sunflower breeders and scientists.