The effects of olive fly damage, olive storage, harvest date, olive grove plot and their interactions on the microflora associated with olive paste and oil acidity were studied. Microflora and oil acidity were significantly affected by the four studied factors and by several interactions between them. Fly damage and olive storage interacted sinergically increasing oil acidity. The relationship between fly damage and oil acidity was lineal although sometimes it was not significant depending on microflora populations. The relationship between microflora populations and oil acidity fitted to a logarithmic model. Major microorganisms in olive paste were bacteria (Xanthomonas), yeasts (mostly Torulopsis and Candida) and in a smaller measure moulds (mainly Fusarium and Penicillium). Results overall suggest that a qualitative damage threshold based on the percentage of damaged fruits in order to infer oil acidity may be unfeasible in most instances.