The effect of chain length and unsaturation on the haemolytic properties of cereal resorcinolic lipids, (5-n-alk(en)ylresorcinols), was studied using isolated saturated, monoenoic and dienoic homologues. The haemolytic activities of the homologues studied were proportional to the degree of the side chain unsaturation and inversely proportional to the chain length. At temperatures close to physiological of animal organisms the most active were mono- and di-enoic homologues of 5-n-heptadecyl and 5-n-nonadecyl resorcinols. The results might point to the importance of short-chain cereal resorcinolic lipids in animal and human nutrition.