The suitability of three acrylic resins for the immunoelectron microscopical localization of cell surface and cytoskeletal antigens in surgically excised, immersion fixed human breast cancer, using an immunogold system, has been assessed. Good localization of milk fat globule membrane was achieved with LR White, LR Gold and Lowicryl K11M, although the embedding schedule for LR White had to be modified. The best results were achieved with Lowicryl K11M. Only scanty labelling of actin and cytokeratin was seen in LR White embedded tissue, whereas there was clear localization in LR Gold and Lowicryl K11M embedded samples. Tubulin and alpha-actinin was detected at low level in tissues in the low temperature embedding resins, but not in LR White embedded samples. The morphology of the latter was poorer, and there was greater variability in ultrastructure and labelling. Of the two low temperature embedding resins, Lowicryl K11M gave slightly better results. However, the advantages could be outweighed by the problem incurred in achieving the low temperatures, and by poorer handling properties than LR Gold.