Abstract: A steplessly adjustable hydrostatic-mechanical composite transmission in which an input shaft is connected to one shaft of a multishaft summing transmission and to one unit of a hydrostatic transmission whose two units are connected in a hydraulic circuit. One of the hydrostatic units is of the variable displacement type while the other is of the constant displacement type and can be connected by selective actuation of respective clutches to two other input elements of the multishaft planetary summing transmission. The latter has, in accordance with the invention, two output members, each of which is connected to a respective input shaft of an after transmission which can be of the planetary or fixed gear pair type. The latter transmission can also be used to effect reversing of the output shaft which is driven thereby.