Minimal deviation adenocarcinoma (MDA), or adenoma malignum, of the uterine cervix is a diagnostically problematic disease because of the difficulty in differentiating it histologically from normal cervical glands. To evaluate the use of mucin phenotyping for differentiating MDA from other conditions, we performed alcian blue pH 2.5/periodic acid-Schiff (AB-PAS) staining and high iron diamine (HID)-AB staining on routinely processed sections of 11 MDAs, 20 unremarkable cervical glands, 9 cervical glandular hyperplasias occurring in association with mucinous ovarian tumors, and 41 conventional cervical adenocarcinomas. In all 11 MDAs and 11 conventional cervical adenocarcinomas, the tumor cell cytoplasm was stained diffusely red by PAS, indicating that MDA cells produce neutral mucin almost exclusively. The amount of acid mucins, both sulfomucin and sialomucin, was decreased markedly by HID-AB. For four MDAs, preoperative biopsy specimens also showed diffuse cytoplasmic neutral mucin. In contrast, the cytoplasm of constituent cells was stained purple to violet by AB-PAS in all unremarkable cervical glands and glandular hyperplasias, indicating that both acid and neutral mucins were produced in equal amounts, sulfomucin being stained predominantly by HID-AB. Of the 30 conventional cervical adenocarcinomas, 28 showed both acid and neutral mucins and two showed acid mucin only in goblet cells, or in part of the cytoplasm or cell surface of constituent cells, where acid mucin consisted predominantly of sulfomucin in 14 and sialomucin in 16. AB-PAS and HID-AB are simple and orthodox histochemical methods which are effective for differential diagnosis of MDA and can contribute to its early detection and treatment.