Abstract
The polypeptide heterogeneity of the chloroplast envelope has been compared with these of other fractions of Spinach chloroplasts: thylakoïds and stroma by means of SDS‐polyacrylamide gel electrophoresis. The envelope electrophoretic pattern shows many polypeptides whose mobility differ from those of the thylakoïds. The possible identity of the small subunit of RudPcarboxylase with a polypeptide of the chloroplast external membrane is discussed.