Soluble, biologically-active recombinant ricin B chain has been produced by expressing B chain-encoding DNA in heterologous eukaryotic or prokaryotic hosts. N-Glycosylated recombinant ricin B chain expressed in Xenopus oocytes bound to both immobilized asialofetuin and immobilized lactose. Non-glycosylated ricin B chain expressed in either E. coli or in tunicamycin-treated oocytes did not bind to immobilized lactose. However, it did bind to asialofetuin, and increasing concentrations of free lactose did not reduce this asialofetuin binding dramatically, in contrast to the effect of free lactose on the binding of either glycosylated recombinant B chain or native ricin B chain.