The invention pertains to a hoisting platform system which is usable in the construction of high rise buildings Included in the system are two I-beams which are mounted on a higher floor of the building under construction which has been finished already. The two I-beams are mounted in a cantilevered fashion with one section jutting forward from the higher floor and another section being attached to the higher floor by several post jacks on top of the I-beams and against the ceiling of the next higher floor. On the forward section there is mounted a pair of A-frames having a cross beam mounted at their tops which in turn has a winch mounted thereon. A movable transfer deck is located between the I's of the two I-beams and can be moved to a position interior of the building once a load is placed thereon. The winch can also be located on the higher floor and idler sheaves can be used on top of the cross beam. The winch is a hydraulic winch which is powered by a hydraulic pump which in turn is powered by an internal combustion engine. There a variations of the A-frames, because a pair of single support struts can be used, which are articulated relative to the two I-beams.