The development of pneumococcal ( Pn ) polysaccharide-protein conjugate vaccines for prevention of invasive disease and otitis media in young children caused by prevalent Pn types has made necessary standardization of assay methods for estimation of Pn polysaccharide ( PS ) antibodies. It is therefore important to have a single reference serum standardized to multiple Pn types. The Pn reference serum now available from the FDA is lot 89SF. We have used C-S, whereby the assigned antibody value for one type is used as the reference for another type, to determine antibody concentrations in the 89SF reference serum to new Pn types and to confirm antibody values assigned by other methods. For C-S, we used methylated serum albumin comixed with PS for adsorption of each Pn type PS to the ELISA plate. Different Pn PS types were coated in the wells and dilution curves for Lot 89SF gave parallel slopes for all types tested. Types 1, 4, 6B, 7F, 9V, 14, 18C, and 23F were individually used as reference curves to calculate IgG values for other types, including Types 2, 3, 8, 9A, 9N, 19A, and 19F. The C-S values for each type was taken as the mean value from 8 reference curves. C-S means were compared to previously assigned IgG values by calculating a ± 20% CV ( Quataert et al., 1995 ). Our results suggest that the C-S method maybe used to determine antibody values for other Pn types.