Fluorescent lectin binding to cell surfaces was quantitatively analysed by flow cytometry on mortal human breast epithelial cells MCF-10M, the immortalized cell line MCF-10A derived from MCF-10M and sublines of MCF-10A transfected with the neomycin resistance gene (MCF-10Aneo), the c-Ha-ras protooncogene (MCF-10AneoN), or transfected and transformed with the c-Ha-ras activated oncogene (MCF-10AneoT). Immortal MCF-10A cells bound 10-fold more peanut agglutinin (PNA) and soy bean agglutinin (SBA) than did MCF-10M cells. Transformed MCF-10AneoT cells bound approximately ten times more PNA than did non-transformed cells transfected with protooncogene (MCF-10AneoN). Treatment of the transfectants with neuraminidase abrogated the differences in PNA-binding and reduced the differences in SBA binding. SDS-PAGE separation of PNA binding glycoproteins revealed different patterns for all MCF-10A derived sublines.