Bromine is one of the most abundant of the recognized trace elementsin the biosphere, belongs to the halogen group. Inorganic bromide is theionic form of bromine exerting its toxic effects. The new role of bromide asa residue in food and water necessitated its broad toxicological evaluation.This study was conducted to demonstrate the histological, ultrastructural andmorphometric changes that may occur in the thyroid gland of albino rats as aresult of bromide administration in variable doses.26 adult male albino ratswere divided into 2 groups; Control group (n=6) and experimental group(n=20) further subdivided into two subgroups: A and B, 10 rats each. Eachrat in experimental subgroups received daily orally 0.15mg and 1.5mg KBrrespectively dissolved in 15ml of drinking water for 66 days. Thyroidspecimens were stained with Hx&E, PAS and toluidine blue stains. Ultrathinsections were prepared for E/M examination. Area % of colloid wasmeasured in PAS stained sections and statistical analysis was performed. Itcould be concluded that bromide induced proliferative as well asdegenerative cellular changes of the thyroid follicles and interfollicularfibrosis with reduced colloid production suggesting hypofunction of thethyroid gland with decreased secretion of the thyroid hormones. The changeswere dose dependent and more evident in high than in low dose of bromide.