Sensitization to olive oil is seldom reported in the literature. By use of epicutaneous tests a delayed type of hypersensitivity to pure freshly-prepared olive oil could be demonstrated in two patients. Patch tests with certain major constituents of olive oil; the methyl ester of linoleic acid, the glyceryl ester of palmitic acid, the glyceryl ester of stearic acid, glyceryl trioleate and glycerids of arachidic acid, appeared to be negative. In one patient a weak reaction to balsam of Peru was found. It is concluded that sensitization to olive oil must be taken into consideration, especially when it is used as a vehicle in patch testing.