The effects of diets containing olive oil, corn oil-ethyl erucate (1:5), rapeseed oil (B. campestris) or zero-erucic rapeseed oil (var. Canbra) on the tissue fatty acids of the rat were investigated. Greatest deposition of erucic acid occurred in the adrenals and decreasing amounts were found in the plasma, heart, spleen, kidney, liver, erythrocyte, testis and brain. Less erucic acid but more eicosenoic acid was deposited from dietary B. campestris oil than from the corn oil-ethyl erucate diet. The relatively high linolenic acid contents of the rapeseed oils resulted in competitive inhibition of linoleate metabolism producing lower concentrations of ω6-polyunsaturated acids in animals receiving these oils