The effect of concentration, insect age, time of day, and length of previous exposure on the response of olive fruit fly,Bactrocera (Dacus) oleae(Gmelin), males to pheromones was studied under laboratory conditions. Concentrations of 0.05, 0.08, 0.1, 0.5, 1.0, 10, 50, 100, 200, 500, and 1,000 μg on Whatman no. 1 filter paper were tested. Male response increased with concentrations from 0.05 to 10 μg and decreased with those higher than 10 μg up to 1,000 μg. The log of concentrations and the corresponding insect responses had a positive linear relationship for the first range of concentrations and a negative linear relationship for the second range of concentrations. Response to the concentration with maximum male response (10 μg) appeared on the third day after adult emergence, increased gradually up to the sixth day, and dropped gradually thereafter. At the age of 35 d, a low response was still present in the flies. Males responded to pheromone during the last 4 h of the light period at a photoperiod of 14:10 (L:D) h. Response increased toward the end of this 4-h period. Response to the concentration of 10 μg decreased significantly after 1 min of continuous exposure to the pheromone, but increase of concentration did not increase the response of these insects.