Among bullous diseases, pemphigus vulgaris (PV) is a classical variety of this type of skin disorders. To establish the real prevalence of thyroid abnormalities in such a disease, a prospective study was developed. For this reason, thyroid evaluation was performed in 15 consecutive patients who attended the Dermatology Clinic for PV and in a group of 15 healthy volunteers (Control Group) matched by age and gender. Thyroid function was evaluated by measuring T3, T4 and TSH. The presence or absence of goiter was searched by palpation, while thyroid autoimmunity was investigated through the assay of thyroperoxidase antibodies (TPO-Ab). In each group there were 9 women and 6 men, aging 25-65 years (mean = 48.3 y) in the PV Group, and 25-69 years (mean = 45.4 y) in the Control Group. It was found that 7 patients (46.6%) of the PV Group and 1 subject (6.7%) of the Control Group (p < 0.015) disclosed thyroidal alterations. Positive titers of TPO-Ab were observed in 6 patients with PV and in one volunteer. Goiter and subclinical hypothyroidism were found in one PV patient with negative TPO-Ab. Out of the total 7 cases with positive TPO-Ab, only a PV patient had an overt Hashimoto's thyroiditis. All other cases had only the presence of thyroid auto-antibodies without clinical evidences of chronic thyroiditis. It is concluded that PV is highly associated with primary thyroid disorders, mainly with positive titers of TPO-Ab, although most patients do not present overt clinical thyroid disease.