The evolution of resistance is a major threat to the efficacy of fungicides. Therefore, to achieve more durable crop protection, we must understand the evolutionary processes driving resistance, in order to apply more effective strategies to manage the risk. The inherent resistance risk of a fungicide depends on the evolutionary accessibility and overall fitness of resistant genotypes, while the inherent resistance risk of a pathogen depends on its adaptive potential, but the overall risk in practice also depends on crop and disease management. In order to design optimal resistance management practices before resistance has evolved in the field, we must predict the evolution of resistance: greater understanding of the adaptive landscapes and fitness trade-offs underlying resistance evolution will improve such predictions, but it is also important to understand that resistance evolution will be less predictable for some fungicide groups than others.