In breast cancer, the most interesting sites showing the regional spread of the disease are the axillary and internal mammary lymph nodes. Monoclonal antibodies are specific in detecting tumor metastases. The aim of this study is to present a simple method whereby the immunolymphoscintigraphic approach is introduced whether bimanually or parasternally. Twenty consecutive female breast cancer patients were imaged with 99mTc-labeled monoclonal intact IgG1 antibody (BW 431/26, Marburg, Federal Republic of Germany), which reacts with carcinoembryonic antigen. The labeling yield was in 10 cases over 98%. The patients had a suspicion of scar recurrency, skin metastases, or palpable lymph node affixions. The patients were imaged twice after bimanual s.c. injections (at 2-3 h and 20-22 h); the bimanual injections were given into first and fourth interdigital interstitial spaces and in one case parasternally following Sappey's lines. A total of 105 lesions in 18 patients were detected. Twenty-five lesions in 18 patients were verified cytologically or histologically. Sensitivity of morphological data was 84%. In supraclavicular and axillary lymph node regions the sensitivity was 90% and the specificity 88% compared to other findings. Most of the undetected lesions were skeletal. The carcinoembryonic antigen concentration in serum had no correlation with the findings. The human anti-murine antibodies showed in two patients of 15 elevated response. This immunolymphoscintigraphy method could be of clinical importance because it enables detection of both regional and systemic lesions in a common type of cancer. The method is sensitive, except for bone lesions, and might be applied for screening purposes in selected patients.