A hydraulic power transmission including a compact external oil pressure takeoff apparatus which houses therein a hydrostatic transmission, and attaches thereto a charge pump. The transmission is capable of supplying operating oil and of taking out external oil pressure. Specifically, part of the discharge oil from the charge pump is adapted to be taken out from the housing so as to omit the need for an external takeout pump. An oil filter is disposed on the exterior of the housing, thereby facilitating maintenance of the hydraulic power transmission.