Abstract: A pressure compensating mixing valve incorporating a flow control spool has an equalizing passage interconnecting opposite end zones of the spool, to reduce or obviate the need for connecting the respective end portions of the spool to pressure fluid supplies, such as the respective valve outputs. This reduces the significance of spool seals, owing to equalization of pressure between certain pressurized zones, so that seal leakage is of lessened adverse significance. Also valve malfunction due to silting-up or liming-up is made less probable.