Bacillus thuringiensis, isolate 114A, was used intoxicity experiments against the wild population of the olive pestBactrocera oleae (Gmelin). In laboratory experiments, sporesand crystals of the B.t. were delivered to the insects withthe food. Longevity, oviposition period, number of eggs produced, andpercent hatch were recorded. Olive fruits from the oviposition testwere dipped into a suspension containing spores and crystals ofB. thuringiensis 114A after the eggs were deposited. Infield experiments, four to six sprayings per year of B.t.114A isolate were applied for three successive years. It was foundthat, in addition to the longevity of B. oleae, theoviposition period, number of eggs and percent egg hatch decreased.Also, the percentage of pupation and emergence was reduced when olivefruits with eggs in their mesocarp were dipped in the solution ofspores and crystals. Field applications with the toxins of 114A isolateof B. thuringiensis have resulted in significant protectionof the olive production.