The disclosed invention relates to the use of esters of unsaturated, physiologically active fatty acids as nutrient media for cell cultivation and, more particularly, as a substitute for foetal bovine serum. In one aspect, the esters comprise more than 50 mol-% of physiologically active fatty acids containing 16 to 24 carbon atoms and 2 to 5 double bonds as the acid component and a lower C1-4 alcohol, preferably ethanol, or a sterol as ester component. In another aspect, the esters comprise a transesterification product of natural or synthetic oils or a mixture of such oils having greater than 50 mol-% of unsaturated, physiologically active fatty acids, based on the acyl group, and a lower C1-4 alcohol or a sterol. In a further aspect, the esters are used together with sterols, phospholipids and/or vegetable proteins or are liposomally encapsulated.