Antisera were made in rabbits to seed extracts from 12 different species in 7 different genera of the conifer family Pinaceae. The immunogens were characterized as mainly protein in nature. The Ouchterlony double diffusion technique was used to measure intra- and intergeneric antigenic distances. The antigenic distances were used to calculate the average rate of protein evolution. Protein evolution has proceeded at about the standard rate found in other groups of organisms. By contrast, chromosomal evolution has proceeded very slowly in the Pinaceae. Possibly, the remarkably slow anatomical evolution which is a characteristic feature of Pinaceae is ascribable to their slow chromosomal evolution. Antigenic distances were also used to derive possible phylogenetic relationships. A close relationship between Larix (larch) and Pseudotsuga (Douglas-fir) was inferred.