The participation of hepatic Golgi apparatus in the intraceUular transport of blood-destined proteins has been analyzed using Golgi fractions enriched in c/s and trans components of the Golgi apparatus.SDS-polyacrylamide gel electrophoresis of the liver Golgi fractions showed several proteins corresponding in relative proportions and mobilities with serum proteins. After a pulse injection of labeled leucine, the secretory content of the c/s Golgi fraction was labeled earlier than the trans Golgi fraction. Taken together, the results show the participation of the liver Golgi apparatus in the secretion of most of the serum proteins and provide documentation for a sequential progression of secretory protein through the c/s and trans components of the Golgi apparatus.