Rat or hamster adrenocortical cells contain a network of filaments mostly 40-80 A in diameter, which is particularly evident at the cell periphery. In frozen sections, adrenocortical cells fix (particularly at their periphery) anti-actin autoantibodies present in sera of patients with chronic aggressive hepatitis. It is concluded that the peripheral network of adrenocortical cells contains contractile proteins (at least actin) and the implication of such proteins in steroid secretion is discussed.