Ganglioside lactams are potentially useful analogs of ganglioside lactones, which are highly immunogenic derivatives of gangliosides. The lactam corresponding to the G(M3)-lactone saccharide has been synthesized by sialylation of a suitably protected lactose derivative carrying an azido group in the 2’-position, followed by reduction and ring closure to form G(M3)-lactam. Glycosylation in the 4-position of the central saccharide unit gave the G(M2)- and G(M1)- lactam saccharides. By a similar route, a 2-azido-Gal derivative was sialylated and treated as above to give the G(M4)-lactam saccharide. Deprotection gave the G(M2-4)-lactam saccharides in water soluble form, whereas attempted deprotection of the G(M1)-lactam caused its degradation. The G(M3)-lactam saccharide was coupled to ceramide, to afford the ganglioside lactam analog, and via a spacer to bovine serum albumin (BSA). The BSA conjugate was used as immunogen to raise monoclonal antibodies that cross-reacted with G(M3)-lactone. The antibodies were used in a histological staining of murine melanoma cells, clearly showing the presence of G(M3)-lactone on the cell surface. Keeping the G(M2-4)-lactam saccharides in D2O at 37 degrees C for 1 month caused marginal (0-11%) hydrolysis of the lactam ring.