Objective To explore the diagnostic value of subacute thyroiditis by fine needle aspiration cytology(FNAC).Method 3665 patients with thyroid disease were detected by FNAC method in 8 years(from Feb 1990 to Dec 1998).Results 353 cases(9 63%) of subacute thyroidits were definitely diagnosed by FNAC with vital staining.Conclusions As compared with other clinical examination including CT,ultrasonic B and radioimmunological assay.FNAC test is all the more simple,safe and valuable diagnostic method for subacute thyroiditis.