This study investigated the influence of UV-B radiation (280-320 nm) on survival of Candida oleophila strain O, an antagonist yeast that prevents postharvest diseases caused by Botrytis cinerea and Penicillium expansum on apple and pear fruits. Lethal doses (LD 50 and LD 90 ) were, respectively, 0AE89 and 1AE45 Kj m )2 for in vitro exposure and 3AE06 and 5AE5 Kj m )2 for in vivo exposure. A screening test of UV-B protectants for strain O was also evaluated under in vitro and in vivo conditions. The in vitro results showed that sodium ascorbate (0AE1% and 0AE01%), riboflavin (0AE1%) and uric acid (0AE1% and 0AE01%) were the most effective and most suitable protectants. However, only riboflavin (0AE1%) and uric acid (0AE1%) were effective under in vivo conditions. The efficacy obtained with strain O against P. expansum, when subjected to UV-B radiation, was 75AE0% and 49AE2% for pathogen concentrations of 10 5 and 10 6 spores mL, respectively. Adding riboflavin to strain O gave a similar efficacy (64AE2%). Applying strain O together with uric acid (0AE1%) was less active (47AE7%). Nonetheless, its efficacy when applied with the antioxidants sodium ascorbate (71AE1%) or ascorbic acid (82AE5%) was the greatest. Riboflavin and uric acid were the most cost-effective protectants, and could be included in the final formulation of strain O when applied preharvest.