The aim of this study was to determine whether the paraoxonase (PON1) status, i.e. PON1 activities and phenotypes (AA, AB and BB), and its relationship with lipid status are different in patients with type II diabetes as compared to healthy population. Diabetic group comprised 175 patients with type II diabetes mellitus (94 men and 81 women) who came to their regular control examination and took the oral glucose tolerance test. Patients with type II diabetes mellitus diagnosis for 12 years on average were on peroral antidiabetics, or insulin or diet, and 3 patients had no therapy prescribed yet. Control group comprised 114 apparently healthy individuals (28 men and 86 women) who were not on any medication. The paraoxonase activity was measured with 2.0 mmol L-1 paraoxon in the absence and in the presence of 1.0 mol L-1 NaCl, and with 2.0 mmol L-1 phenylacetate. Both activities were measured spectrophotometrically at 37 oC in 0.1 mol L-1 Tris-HCl buffer, pH = 8.0, containing 2.0 mmol L-1 CaCl2. Sera of diabetic and control subjects were assigned to the paraoxonase phenotypes on the basis of the basal paraoxonase activity distribution. We assigned 45% sera of male and 49% sera of female diabetic patients, and 64% sera of both genders of the control group to the AA low activity phenotype. There were no differences in paraoxonase activities between the gender- and phenotype-matched diabetic and control groups. Enzyme activity against the phenylacetate was higher and phenotype-dependent only in diabetic patients. In contrast to AA phenotype individuals, total cholesterol and LDL-cholesterol in the female diabetic group and triglyceride concentration in the male diabetic group assigned to pooled AB and BB phenotypes were higher than in the corresponding controls. It follows from PON1 phenotype distribution that less antiatherogenic paraoxonase B allele is more frequent in type II diabetes mellitus than in the healthy population. Their lipid status is more atherogenic, which could indicate a risk of premature atherosclerosis.