A two-year experiment on the influence of Dacus oleae infestation on phenolic composition of virgin olive oil was carried out. The phenolic compounds were detected by HPLC-UV in oils obtained by olive samples with different degrees of insect larval development. The ratios of the total phenolic compounds to the sum of o-diphenoles were studied, as the latter are the only components of phenolic fraction which provide antioxidative activity. This ratio is particularly high in oil obtained from olives in which the parasite has reached its highest degree of larval development. Moreover, the ratio further increases when olive damage is increased by negative climatic conditions