The present investigation was undertaken to demonstrate saturable β2‐adrenoceptor binding sites on cell membranes of bovine lymphocytes by means of the non‐selective antagonist (3H) dihydroalprenolol. Although the classical density gradient centrifugation technique was used as described for the isolation of these cells from human blood, striking differences in binding characteristics were observed. It is suggested that differences in physical properties of blood might be responsible for these phenomena. Since receptor density and affinity of β2‐adrenoceptors in lymphocytes are used in human medicine (and will be in the future in veterinary medicine) for correlation with several physiological and pathophysiological conditions, attention is drawn to the effect of dilution of blood during the preparation of these cells; in lactating cows, the best results were obtained with the dilution 1: 0.5.