Polyamines are low molecular weight organic cations, necessary for cell proliferation and implicated in numerous biochemical events. Their light microscopical distribution has previously been studied by the use of two fluorescence cytochemical methods. With the aid of an antibody recognizing the two main polyamines, spermidine and spermine, we now report on their immunocytochemical localization in animal tissues. Polyamine immunocytochemistry was found to require very well controlled conditions of fixation in order to prevent diffusion, loss and redistribution of endogenous polyamines. Moreover, in certain cellular compartments, polyamine immunoreactivity was masked by proteins, necessitating proteolytic pretreatment of sections prior to staining. The fluorescence cytochemical methods, employing low molecular weight reagents, did not require such unmasking. The results of the optimized immunocytochemical procedure were in complete agreement with the results obtained by the fluorescence cytochemical methods. Although fluorescence cytochemistry, is simpler and quicker to perform than immunocytochemistry, the latter technique may be extended to studies of polyamines at the ultrastructural level.