To assess vascular compliance in patients with antiphospholipid syndrome (APS), or antiphospholipid antibodies (aPLs) positivity in comparison to healthy people and diabetes mellitus patients. Twenty-five patients with APS or aPLs, 33 healthy people (HP), 28 patients with diabetes mellitus (DM) underwent pulse wave analysis. Data calculated included the small artery elasticity (SAE), large artery elasticity (LAE) and systemic vascular resistance (SVR). Statistical analysis was performed as appropriate. The patient group was divided into two subgroups: APS-1 with warfarin treatment, and APS-2 without warfarin treatment. All patients and healthy subjects were matched by gender, body mass index and lipid profiles. Patients in APS-1 group were significantly younger in comparison to three other groups. After the adjustment for age, we found that SAE in APS-1 group did not differ from SAE in the HP group (6.4+/-1.8 ml/mmHg x 100 and 5.54+/-3.4 ml/mmHg x 100, respectively, P>0.05). In contrast, SAE in the group APS-2 was significantly lower (3.41+/-1.2 ml/mmHg x 100) than in the APS-1 and was almost equal to SAE in the DM group (4.2+/-2.37 ml/mmHg x 100). The SAE in the APS-2, DM and HP groups was inversely correlated with age, whereas in the APS-1 group we did not find such correlation. This pilot study showed abnormal small vascular elasticity in the patients with positive aPL, relative to the healthy subjects. The APS patients, treated with warfarin had the normal vascular function. This data support the hypothesis that APS may be associated with diffuse changes in the arterial wall, and may be a risk factor for atherosclerotic disease.