[en] A variety of radioiodination methods is available in the literature depending upon the nature of organic compound to be labeled, however only few can completely fulfill manufacturing requirements.Ideally a selected method should be one which offers maximum benefits like regioselectivity, minimum reaction steps, minimum reaction time, high radiochemical yield and high specific activity. In this review radioiodination techniques were critically analyzed. Advantages, drawbacks, possible mode of action and special reaction conditions required to get high radiochemical yield were taken into account. The influence of iodine introduction on physicochemical properties, in vivo or in vitro pharmacological properties of pharmaceutical due to increase of lipophilicity were discussed along with examples. (author)