Introduction: the association of thyroid abnormalities with systemic lupus erythematosus (SLE) is not well established. Objective: to study the prevalence of thyroid dysfunction in hundred lupus patients and evaluate a possible association between thyroid dysfunction and SLE disease activity. Methods: a total of one hundred patients with SLE underwent assessment for clinical and laboratorial thyroid abnormalities. Clinical activity was assessed using the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Results: seventeen patients (17%) had abnormal thyroid function by laboratory testing, which included ten patients (10%) with subclinical hypothyroidism, two patients (2%) with subclinical hyperthyroidism, four patients (4%) with primary hypothyroidism and one patient with serum thyroxine below the normal range. Regarding antithyroid antibodies, six patients were positive, as follows: four (4%) for antiperoxidase, one (1%) for antithyroglobulin and one (1%) for both antibodies. SLE disease activity was not significantly different between groups, regardless of the presence of thyroid dysfunction. Conclusion: these results show that thyroid abnormalities are frequently found in SLE patients. However, it does not appear to be an association between thyroid abnormalities and SLE clinical disease activity.