Abstract: A novel apparatus is disclosed for the alternate filling and evacuation of all wells simultaneously of a multi-well microplate. The apparatus consists of a flat, horizontally disposed vacuum chamber having an upper plate and a lower plate, with a rectangular array of tubes passing through the latter such that two tubes are aligned with each well of a microplate, one for filling and the other for evacuation. The microplate is supported below the vacuum chamber with the tubes in proper alignment, and means are provided for bringing the microplate and the tubes in close proximity, for applying a vacuum to the vacuum chamber for evacuating the wells, and for supplying pressurized wash fluid to the filling tubes. The apparatus provides a faster washing process for microplates, and is more reliable and efficient than devices already known for the same or similar purposes.