Recent studies have further elucidated the association between blood pressure and albumin excretion in insulin-dependent diabetes mellitus (IDDM) patients with (i) normal urinary albumin excretion (UAE), and (ii) moderate microalbuminuria (20 to 70 micrograms/min). In a study comprising 117 normoalbuminuric (UAE < 20 micrograms/min) patients we performed 24-hour ambulatory blood pressure monitoring (AMBP), and short-term power spectral analysis of RR interval oscillations. In comparison with the group with a UAE below the median, patients with UAE above the median were characterized by: significantly higher 24-hour systolic and diastolic AMBP, significantly reduced short-term RR interval variability, and significantly higher HbA1c. In a double blind study, normotensive IDDM patients with moderate microalbuminuria (20 to 70 micrograms/min) were randomized to either lisinopril (20 mg once a day, N = 12) or placebo (N = 10) for two years. In the lisinopril group there were significant reductions in 24-hour systolic and diastolic AMBP compared to the placebo group. Lisinopril did not attenuate the diurnal blood pressure variation. UAE tended to be reduced in the lisinopril group. A significantly positive association between changes in AMBP and changes in UAE was present in the placebo group in contrast to the lisinopril group. Changes in UAE were strongly and positively associated with changes in filtration fraction in the lisinopril treated group. In conclusion, interactions between albumin excretion, blood pressure, autonomic function, and glycemic status are already detectable within the normoalbuminuric range in IDDM patients. Angiotensin converting enzyme inhibitor (ACEi) treatment in a small group of normotensive IDDM patients with moderate microalbuminuria reduces blood pressure without attenuating diurnal blood pressure variation, tends to reduce albumin excretion, and abolishes the association between changes in UAE and changes in blood pressure observed in the placebo group. ACEi intervention in selected normoalbuminuric high risk patients (high-normal UAE, high-normal blood pressure, and poor glycemic control) would be of interest.