Potato (Solanum tuberosum) lectin, which is a very highly glycosylated glycoprotein, has been completely deglycosylated by use of the trifluoromethanesulphonic acid reagent described by Edge, Faltnek, Hof, Reichert & Weber [(1981) Analyt. Biochem. 118, 131-1371. This shows that both hydroxyproline-arabinofuranoside and serinegalactopyranoside linkages are hydrolysed. The deglycosylated lectin is still functional and cross-reacts with one component of an anti-(potato lectin) antiserum.