Amiodarone was reported as one of the most effective antiarrhythmic drugs available; however, its use is often limited due to its direct cytotoxicity to the thyroid as proved histologically, ultrastructurally, morphometrically and functionally. Propranolol was found to induce membrane disruption, extensive fibrosis with prolonged administration and altered thyroid function was proven. Minimal changes in thyroid structure with no changes in mean area of colloid or thyroid function tests were recorded with verapamil. Therefore, results of the present study would suggest verapamil as the most suitable and safest antiarrhythmic drug to be used in the treatment of arrhythmias associated with thyroid disorders.