A ballistic type wire printing head comprises a metal front support (11) for guiding the printing wires (23) and supporting a group of actuating electromagnetic units (37, 39, 41) associated with the wires. The armatures (41) of the electromagnetic units are pre-assembled on a disc (40) of plastics material. A rear cover (59) which is also of metal encloses the electromagnetic units and in its interior supports spring spider (58) which co-operates with all the armatures of the electromagnetic units. The electromagnetic units have a common internal, ferromagnetic support (35) from which heat is conducted to the front support (11) and cooling fins (25). In a second embodiment, the printing head also comprises a second group of electromagnetic units associated with another series of printing wires. In that case, an intermediate metal member acts as a cover member for the first group of electromagnetic units and as a support for the second group of electromagnetic units.