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.
El Greco was one of the first painters in Spain to depict the two Christian apostles, St Peter and St Paul, together. This enabled the artist both to reflect on religious concerns and to contrast their different personalities: St Paul is devout and passionate, St Peter gentle and meek. The poses and gestures, the colours and expression, the superb technique, all these emphasize the contrast between the two. This painting comes from the high period of El Greco's creative life, a period during which he executed a whole series of works on the subject of Christ and the Apostles.