The purpose of this study was to examine a possible difference in the 24-h blood pressure (BP) profile between hypertensives with diabetic nephropathy (DN) and those with non-diabetic glomerulopathy (non-DN). We measured 24-h ambulatory BP in 34 type 2 DN and 34 non-DN patients who were hospitalized for the educational program in our hospital. There were no significant differences in 24-h and daytime systolic BP between DN (143 vs. 136 mmHg, NS for 24-h systolic BP) and non-DN (143 vs. 138 mmHg, NS for daytime systolic BP). Although both groups disclosed blunted nocturnal decrease in BP and were classified as "non-dipper" type, DN patients had a significantly higher nighttime systolic BP than patients with non-DN (142 vs. 132 mmHg, p = 0.0217). BP and heart rate (HR) variabilities were also estimated, and patients with DN showed a reduced nighttime HR variability than those with non-DN (4.8 vs. 6.6 beats/min, p = 0.0115). DN patients had an increase in urinary protein excretion (3.0 vs. 1.4 g/day, p = 0.0095) and a decrease in serum albumin concentration (3.1 vs. 3.7 mg/dl, p < 0.0001). Furthermore, urinary protein excretion was significantly correlated with nighttime systolic BP (r = 0.480, p = 0.0031) but not with nighttime HR variability. Taken together, these results demonstrate that the circadian rhythms of BP and HR are affected by underlying diseases and suggest that an elevated nighttime BP level may contribute to the enhanced urinary protein excretion in hypertensives with DN.