The distribution of low density lipoprotein(LDL)receptors in various tissues of rabbit was studied using indirect immunofluorescence staining with monoclonal anti-rabbit LDL receptor antibodies prepared in our laboratory.The results showed that there was specific fluorescence in liver,adrenal cortex,ovary,intestine,bronchus and skin,but in liver and adrenal cortex,the specific fluorescence of the cells was brighter than that in all other tissues.In heart muscle,skeletal muscle and adrenal medulla the fluorescence of the cells was vary faint,especially in brain parenchyma.It suggest that there may be an interrelationship between the LDL receptor activity and the physiological function and metabolism of the tissues.