ABSTRACTThe retention of radioactive noradrenaline (NA) was measured in different organs of immunosympathectomized (I.S.) mice 30 min after i.v. injection of dl‐NA‐7–3H (17.9 or 1.79μg/kg, S.A. 4.7 C/mmole). A striking decrease in the capacity to retain NA‐3H was observed in the heart (1.6 per cent of controls) and the submaxillary gland (4.1 per cent of controls). Immunosympathectomy was only partially effective in the intestine and colon (33 and 47 per cent of normal retention, respectively). By contrast, the retention of NA in the I.S. vas deferens was almost doubled. These data support previous investigations indicating that immunosympathectomy has a differential effect on adrenergic neurons located in different organs. A chromatographic analysis of the distribution of3H among the various NA‐metabolites was undertaken in the submaxillary gland, heart and vas deferens. Metabolites, for the most part methylated, accounted for a larger precentage of the total3H in the extracts from tissues of I.S. animals compared to controls. In the I.S. submaxillary glands of both the mouse and the rat the radioactivity retained after injection occurred mostly in the form of metabolites. Normetanephrine (NM) was predominant in the mouse, while both NM and acid metabolites were significant components in the rat gland. Oxidation to acid metabolites was more extensive in the I.S. heart of the rat compared to the mouse. The chromatography of the retained metabolites in the I.S. vas deferens was not qualitatively different from that of the no