Instrumental neutron activation analysis (INAA) was used to determine the Br and I concentration in the same ten lyophilized and homogenized human thyroid samples prior and after a 20-year storage at room temperature. It was found that long-term storage had no effect on the iodine content. At the same time, the bromine content was about 2-fold lower (p<0.01). It was assumed that possible losses of other halogens can occur under long-term storage of lyophilized biological materials at room temperature.