We make a systematic study of the sacraments in general, from the dogmatic and liturgical point of view. The sacraments are studied as facts of communication between God and men. It begins with an anthropological basis: theory of human communication, phenomenology of religion; and then move on to the communication that God makes of himself in Revelation: creation, the Old Testament and the New Testament. The following is a historical summary of the theological reflection on the sacrament: in patristics, in scholasticism, in the reform and the Council of Trent, in the post-Tridentine and current era. After a brief resumption that shows the centrality of Christ as a fundamental event in the communication of God to man, we move on to the systematic study of the sacrament: definition, institution, efficacy, the rite, the permanent dimension, grace and sacramental life, the sacramentals.