A door system, comprising: two bi-parting, center-opening, bi-directional door panels (12, 14) disposed for counter-rotating swinging movement in a doorway; a synchronizing system operatively associated with the door panels (12, 14); and the synchronizing system being operative to swing the door panels (12, 14) simultaneously selectively outwardly or inwardly of the doorway to open the door panels, and to simultaneously close the door panels, such that the door panels swing through substantially equal angular distances during opening and closing; the synchronizing system including a linkage system, and further including two motion converters, the linkage system and motion converters being operatively associated with the door panels (12, 14); the linkage system including first and second linkages (60, 62), each defining a driven link; each motion converter being drivingly connected to a respective door panel (12, 14) and being operative to convert the motion of a respective driven link to rotary motion, such that rotation of one door panel (12, 14) through a predetermined angular distance, whether inwardly or outwardly of the doorway, simultaneously rotates the other door panel (14, 12) through substantially the same angular distance the first and second linkages (60, 62) lying in the same plane; characterized in that each of the first and second linkages (60, 62) defines a driver link pivotably connected to a connecting link which in turn is pivotably connected to a respective driven link, such that the driver and driven links of the first linkage remain in parallel throughout the operation of the synchronizing system, and the connecting link of the second linkage being disposed at an angle to the connecting link of the first linkage, such that the driven link of the second linkage rotates in a direction opposite to the direction of rotation of the driven link of the first linkage. two bi-parting, center-opening, bi-directional door panels (12, 14) disposed for counter-rotating swinging movement in a doorway; a synchronizing system operatively associated with the door panels (12, 14); and the synchronizing system being operative to swing the door panels (12, 14) simultaneously selectively outwardly or inwardly of the doorway to open the door panels, and to simultaneously close the door panels, such that the door panels swing through substantially equal angular distances during opening and closing; the synchronizing system including a linkage system, and further including two motion converters, the linkage system and motion converters being operatively associated with the door panels (12, 14); the linkage system including first and second linkages (60, 62), each defining a driven link; each motion converter being drivingly connected to a respective door panel (12, 14) and being operative to convert the motion of a respective driven link to rotary motion, such that rotation of one door panel (12, 14) through a predetermined angular distance, whether inwardly or outwardly of the doorway, simultaneously rotates the other door panel (14, 12) through substantially the same angular distance the first and second linkages (60, 62) lying in the same plane; characterized in that each of the first and second linkages (60, 62) defines a driver link pivotably connected to a connecting link which in turn is pivotably connected to a respective driven link, such that the driver and driven links of the first linkage remain in parallel throughout the operation of the synchronizing system, and the connecting link of the second linkage being disposed at an angle to the connecting link of the first linkage, such that the driven link of the second linkage rotates in a direction opposite to the direction of rotation of the driven link of the first linkage.