Abstract: By means of SDS linear gradient polyacrylamide gel electrophoresis, seed protein peptides of 50 species belonging to 10 genera of Pinaceae were analysed. A major peptide possessing molecular weight about 45000 daltons is shared by every species in Pinaceae. There are many peptides of higher molecular weight in seeds, but their content is very low. In order to make a series of quantitative comparisons between any two taxa, we define “peptide distance” as follows: number of different peptides between 2 taxa peptide distance= ------------ total number of peptides in 2 taxa In the following table, the peptide distances of some genera are shown together with other molecular data about Pinaceae.