SEPARATION of pituitary hormones by zone electrophoresis on paper has not proved very successful, possibly due to complex formation between proteins1. Starch-gel zone electrophoresis introduced by Smithies2,3 separates proteins not only by their net charge but also by their molecular size. This procedure has superior resolving power to paper or agar-gel zone electrophoresis and has been successfully applied to the analysis of thyrotrophic hormone4–6. Starch-gel electrophoretic analyses of various standard preparations of anterior pituitary hormones are presented here together with some evidence of the distribution of hormonal activities.