BACKGROUND AND OBJECTIVES Dysfunctional uterine bleeding is an abnormal bleeding from the uterus in absence of organic disease of genital tract and demonstrable extragenital cause. Thyroid dysfunction is marked by large number of menstrual aberrations. This study aimed at detecting thyroid dysfunction and further evaluating in patients with a provisional diagnosis of DUB. METHODS One hundred cases of clinically diagnosed DUB were taken from Gynaecology OPD and in patients of OBG Department VIMS, Bellary. All patients from puberty to premenopausal age groups presenting as menorrhagia, acyclical metropathia, polymenorrhagia, metrorrhagia, oligomenorrhoea, polymenorrhoea and hypomenorrhoea were tested for their thyroid function by T3, T4, TSH estimations in their serum. Patients who had clinical symptoms and signs of thyroid disease, was on hormonal treatment, IUCD users, or had bleeding disorders were excluded from the study. RESULTS A 23% of patients who were studied had thyroid dysfunction of which 13% of patients had subclinical hypothyroidism, 7% of patients had hypothyroidism and only 3% of patients had hyperthyroidism. The commonest bleeding abnormality in subclinical hypothyroid patients were polymenorrhoea and menorrhagia. All hyperthyroid cases were oligomenorrhoeic. CONCLUSION Both subclinical hypothyroid and profoundly hypothyroid cases together were the commonest thyroid dysfunction and menorrhagia was their commonest menstrual abnormality. So this study concludes that biochemical evaluation of thyroid functioning should be made mandatory in all provisionally diagnosed cases of DUB to detect thyroid dysfunction.