OH and HO₂ control the transformation of air pollutants and O₃ formation. Their implication for air quality over the climatically sensitive Mediterranean region was studied during a field campaign in Cyprus. Production of OH, HO₂, and recycled OH was lower in aged marine air masses. Box model simulations of OH and HO₂ agreed with measurements except at high terpene concentrations when model RO₂ due to terpenes caused large HO₂ loss. Autoxidation schemes for RO₂ improved the agreement.