Background: Diagnosis of thyroiditis is rather difficult since it can simulate any other thyroid disease. This study was 
conducted to determine the clinico-pathological features of thyroiditis and to evaluate the efficacy of the various modalities utilized for diagnosis of the disease. 
Patients and Methods: The study included 59 patients with the clinical diagnosis of thyroiditis. Ten patients had subacute thyroiditis (SAT) and 49 had chronic thyroiditis (CHT). Investigations included serum levels of T3, T4 and TSH, antichromosomal antibodies (AMA), anti-thyroglobulin antibodies (ATGA), Ultrasonography for the thyroid gland and FNAC. 
Twenty-four patients improved by conservative treatment while 35 needed thyroidectomy where histopathology for the 
excised glands confirmed the diagnosis of thyroiditis. 
Results: The mean age of patients with SAT was significantly lower than that of those with CHT (28.13±5.82 years vs 
44.1±8.36 years, respectively) (t= 5.62, p=0.002). Seventy one percent of patients with CHT had concomitant autoimmune disease, and nine of the 10 patients with SAT had history of recent upper respiratory tract infection. There was an obvious tendency towards hypo-thyroidism associated with CHT and towards hyperthyroidism associated with SAT. Both AMA and ATGA were significantly higher in patients with CHT as compared to those with SAT (P<0.05). Hypoechoic sonographic pattern of the goiters formed the majority in both groups (33/49 and 8/10 for CHT and SAT respectively) (X2=26.612, P<0.001). FNAC could diagnose 30 out of 49 cases of CHT with a sensitivity of 59.2% a specificity of 90%, a positive predictive value of 96.7% and a negative predictive value of 31%. It did not diagnose any of the ten SAT. Conclusions: Diagnosis of thyroiditis requires a high index of suspicion. A history of concomitant autoimmune disease could associate CHT. An upper respiratory tract infection may well precede a SAT. CHT is associated with a significant rise of AMA and ATGA. Hypoechoic sonographic pattern is found in a significant number of patients with thyroiditis. FNAC is specific yet insensitive test for the diagnosis of thyroiditis.