The disulfide bond pattern of Trimeresurus stejnegeri lectin (TSL), a new member of the C-type lectin family, was determined by mass spectrometry. Four intrachain disulfide bonds of TSL, Cys3-Cys14, Cys31-Cys131, Cys38-Cys133 and Cys106-Cys123, and two interchain linkages, Cys2-Cys2 and Cys86-Cys86, were determined. Three strategies were used in this work. One intrachain (Cys106-Cys123) and one interchain (Cys86-Cys86) disulfide linkages were detected by standard MS methods. The disulfide bonds Cys2-Cys2 and Cys3-Cys14 were analyzed using a modified partial reduction procedure and MS/MS. The last two disulfide bonds were characterized by a MS/MS/MS technique. The strategies developed in this work could be applied more generally to detection of disulfide bond patterns. Copyright © 2001 John Wiley & Sons, Ltd.