Total OH reactivity, the total loss frequency of the hydroxyl radical in ambient air, provides the total loading of reactive gases in air. We measured the total OH reactivity for the first time during summertime at a coastal receptor site located in the western Mediterranean basin. Measurements were performed at a temporary field site located in the northern cape of Corsica (France), during summer 2013 for the project CARBOSOR (CARBOn within continental pollution plumes: SOurces and Reactivity) -ChArMeX (Chemistry-Aerosols Mediterranean Experiment). Here, we compare the measured total OH reactivity with the OH reactivity inferred from the measured reactive gases. The difference between these two parameters is termed missing OH reactivity, i.e., the fraction of OH reactivity not explained by the measured compounds. The total OH reactivity at the site varied between the instrumental LoD (limit of detection = 3 s −1 ) to a maximum of 17 ± 6 s −1 (35 % uncertainty) and was 5 ± 4 s −1 (1σ standard deviation) on average. It varied with air temperature exhibiting a diurnal profile comparable to the one of the biogenic volatile organic compounds measured at the site. We observed a fraction of missing OH reactivity during two distinct periods (on average 56 %), associated respectively to transported aged air masses and low-wind speed conditions at the site. We suggest that oxygenated molecules, mostly formed from reactions of biogenic gases precursors, were the major contributors to the missing OH reactivity.