Malignant transformation of cells leads to the synthesis of large asparagine-linked oligosaccharides that exhibit a higher degree of beta 1,6 branching. In rodent and human tumor cell lines and certain human tumors, increased beta 1,6 branching of oligosaccharides has been shown to be associated with metastasis. In addition, this structural change occurs in glycoproteins of stimulated normal human lymphocytes. The leukoagglutinating Phaseolus vulgaris lectin (L-PHA) has a high affinity for tri- and tetraantennary beta 1,6 branches carrying oligosaccharides and has been widely used for the detection of such structures by histochemistry and blotting. We have analyzed a spectrum of normal human and rat tissues using a sensitive silver-intensified lectin-gold technique. Staining by L-PHA was detected in undifferentiated cells of germinative layers of the gastrointestinal and respiratory tract as well as testis. However, differentiated and non-mitotic epithelia in most organs showed strong lectin staining as well. Notable exceptions were the epithelium of the colon and resting mammary gland, which were unreactive with L-PHA. The histochemical studies were supplemented by lectin blotting, which showed the presence of diverse L-PHA-reactive glycoproteins in rat tissues. Our data may be of importance for the use of L-PHA in studies on human malignant tumors.