The two saints, who were strongly associated with each other as the most influential leaders of the early Church. In this portrayal they are shown engaged in an animated discussion. The older, white-haired Peter, wrapped in a golden coloured cloak inclines his head thoughtfully to one side as he looks towards the text being expounded. In his left hand he holds his attribute, the key to the kingdom of Heaven. His right hand is cupped as if weighing up an idea. Paul presses his left hand down firmly on the open volume on the table, his right hand raised in a gesture of explanation as he looks directly at the viewer.
St Peter and St Paul appear separately a great number of times in El Greco's oeuvre and they are depicted with remarkable consistency. Peter is always shown with white hair and beard, and he often wears his yellow cloak over a blue tunic. Paul is always shown slightly balding, with dark hair and beard, wearing a red mantle thrown over a blue or green tunic, which is here just visible at the neck.
There is an earlier version of this composition in the Hermitage, St Petersburg.