SDS-polyacrylamide gel electrophoresis showed some slight quantitative species-dependent differences in total non-histone chromatin proteins and nuclear phosphoproteins (phenol-soluble fraction of non-histone chromatin proteins) but no differences in the DNA-binding non-histone proteins. 2. Comparative studies on DNA and RNA content, and amino acid composition of nuclear phosphoproteins and DNA-binding non-histone proteins of pancreas demonstrated a striking similarity between the two species studied.