The aim of this study was to assess the relationship between homocysteine (tHcy), folate and vitamin B 12 levels, urinary albumin excretion, and arterial blood pressure in patients with noninsulin-dependent diabetes mellitus (NIDDM). Our study was carried out in 33 NIDDM patients (16 men, 17 women) and 16 healthy volunteers as controls (seven men, nine women). Fasting and postmethionine load plasma tHcy levels were assessed, together with folate, vitamin B 12 , and urinary albumin excretion levels. In NIDDM patients, there were correlations between folate and mean arterial pressure (r β«Ψβ¬ β«Ψβ¬ Ψ0.352, P β«Ψβ¬ β«Ψβ¬ .046), folate and systolic blood pressure (r β«Ψβ¬ β«Ψβ¬ Ψ0.437, P β«Ψβ¬ β«Ψβ¬ .013), folate and vitamin B 12 (r β«Ψβ¬ β«Ψβ¬ 0.499, P β«Ψβ¬ β«Ψβ¬ .004), tHcy and vitamin B 12 (r β«Ψβ¬ β«Ψβ¬ Ψ0.348, P β«Ψβ¬ β«Ψβ¬ .04), ln tHcy and ln folate (r β«Ψβ¬ β«Ψβ¬ Ψ0.404, P β«Ψβ¬ β«Ψβ¬ .01), and, lastly, between tHcy, either fasting or postload, and urinary albumin excretion. Patients with elevated tHcy levels had significantly higher diastolic blood pressure (P β«Ψβ¬ β«Ψβ¬ .04) and mean arterial pressure (P β«Ψβ¬ β«Ψβ¬ .03). Otherwise, higher folate values were associated with lower systolic blood pressure (P β«Ψβ¬ β«Ψβ¬ .004) and mean arterial pressure (P β«Ψβ¬ β«Ψβ¬ .02). In addition, NIDDM patients with complications presented higher tHcy basal values than the group without complications (P β«Ψβ¬ β«Ψβ¬ .003). A particular propensity of such patients towards endothelial dysfunction could explain the presence of correlations between these metabolic parameters and arterial blood pressure.