A method for recording blood glucose concentration with use of a continuous sampling technic is described. Sensitivity studies indicate that fluctuations of 3 mg. per 100 ml. or more are reflected on the recording. The major cause of artifact was interruption of flow in the blood sampling tubing or in one of the reagent tubings. Recordings were made during the course of five-hour glucose tolerance tests performed on normal subjects and patients with hyperthyroidism (4), hypothyroidism (1), acute hepatitis (1), and the postgastrectomy syndrome (2). The continuous sampling technic is a practical method to obtain precise temporal and quantitative information relative to fluctuations of the blood glucose concentration under a variety of circumstances.