This work evaluates by a chronobiological approach the relationship between arterial hypertension and diabetes mellitus. Sixteen type II (non-insulin-dependent) diabetic hypertensive males (age 50-60 years, BMI 26 +/- 1, without nephropathy) were selected for the study. Blood pressure (BP) was considered borderline, mild or moderate, systolic and/or diastolic by a single measurement (occasional measurement) according to the Report of the Joint National Committee on Detection, Evaluation and Treatment of High Blood Pressure (1984). Then both dynamic ambulatory BP through a 24-hr span (5300 ABPS Spacelabs) and an oral glucose-tolerance test (100 gm) with serum glucose and insulin measures were carried out. Total insulin area (TIA) and total glucose area (TGA) were computed. Blood-pressure values were analyzed by the Cosinor method, and then percent time of elevation (PTE) and the hyperbaric impact (HBI) were calculated. A statistically significant positive correlation was found between TIA and the mesors of both systolic BP/diastolic BP (p less than 0.05) and HBI (p less than 0.05 and p less than 0.01, respectively).