A scroll fluid device is provided with a synchronizer arrangement that prevents relative rotation between the involute scroll wraps defining fluid working chambers while permitting the wraps to orbit relative to each other to perform work on fluid moved through the device or to expend work through the reaction of fluid moving through the device. The synchronizer comprises axially extending teeth affixed to one of the scroll support end plates interdigited with grooves affixed to the other end plate. The grooves of the synchronizer each have a width that accommodates the orbital excursion of each tooth extending into the groove such that, during orbital movement of one scroll wrap relative to the other, the teeth engage the side walls of the groove to prevent rotation of the scroll wraps relative to each other in either direction. The synchronizer also permits movement of one scroll wrap relative to the other along a line generally extending between the involute centers of the wraps in a direction that reduces the orbit radius.