The results of the assay using rabbits indicate that the efficiency of the method can be considerably improved without loss of precision by omitting the initial and final blood sugar detns. in the conventional bleeding schedule. Considerable economy of time and effort without loss of precision can be accomplished in the assay of insulin by intraven. admn. of the doses and using one bleeding 50 mins. after injn. The potency of commercial insulin prepns. when assayed by the intraven. admn. of the doses showed excellent agreement with the potency detd. by the subcut. admn. of the doses and a bleeding schedule at 0, 1.5, 3 and 5 hrs.