[en] We tried to put the estrogen metabolite to use in tumor imaging. The antibody against estriol 3-sulfate (E₃ 3-S), which was one of the major metabolites of estrogen in hormone-dependent mammary carcinoma, was prepared and the tissue distribution and imaging of human breast carcinoma with anti-E₃ 3-S antibody (Ab) were studied in nude mice. In hormone-dependent breast carcinoma, MCF-7,-bearing nude mice, [¹²⁵I] anti-E₃ 3-S Ab localized in tumor with the percentage injected dose/g of 9.29 ± 3.01 (mean ± SD). This value was significantly high compared with that in hormone-independent breast carcinoma, MDA-MB-231,-bearing nude mice. At 72 h after the administration of [¹²⁵I]anti-E₃ 3-S Ab to MCF-7 bearing mice, tumor/blood, tumor/liver and tumor/muscle ratios were 0.49, 5.02 and 6.83, respectively. These ratios were supposed to be enough for imaging. In radioimmunoscintigraphy, a MCF-7 tumor was clearly visualized at 120 or 168 h post-injection of [¹³¹I]anti-E₃ 3-S Ab