Serum protein types were determined for Canadian Indians belonging to three separate linguistic groups. The Hp1 frequencies were within the range predicted on the basis of the known geographic distribution of haptoglobin types, being less than 0.50 in all but the Siouan group. Transferrin D Chinese was found in approximately 6% of Plains Crees (Algonkians) but was infrequent Canadian Indians or absent in the other groups studied. The Gc2 frequency was low in the Athabascan and Siouan groups and intermediate in Algonkians. The presence of a polymorphism for normal and a fast variant of serum albumin (albumin Naskapi) was confirmed in Algonkians and Athabascans. C5 + variants of serum cholinesterase were found an all three groups. Three pedigrees that provided information on the Gc/albumin linkage were analysed and their lod scores were combined with those from reported pedigrees. Based on the combined data, assuming allelism of different variants, the best estimate of the map distance is 2.5 centimorgans with 95% probability limits 0.9–5.0 centimorgan