To determine the characteristics of the blood pressure circadian rhythm in non-hypertensive type 2 diabetic subjects.Cross-sectional study on 57 individuals with type 2 diabetes without hypertension (31 women and 26 men) and 57 healthy subjects in a control group (29 women and 28 men). High blood pressure, renal or hepatic diseases were exclusion criteria. Using patient activated semiautomatic portable blood pressure recorder (Omron Healthcare Inc., Vernon Hills, Ill 60061), self-measured blood pressure of 24-h was registered. Subjects who blood pressure measures were not appropriately recorded in equal or more than 10% of the lectures were not included.The average systolic and diastolic blood pressure of 24-h was similar between the groups studied. The percentage decrease in the nocturnal systolic/diastolic blood pressure was of 4.6%/1.2% and 3.8%/6.8% for the diabetic women and men respectively, and of 8.6%/9.9% and 6.8%/8.2% in the control women and men. For the last nocturnal and first diurnal hours the systolic/diastolic blood pressure of diabetic subjects showed a lower increase with a higher duration than that observed for the control group.Non hypertensive type 2 diabetic subjects shown both nocturnal blood pressure fall of less than 10% and a lower increase, with prolonged duration in the first diurnal hours, than that observed in healthy subjects.