Abstract: Apparatus for accurately transferring liquids for filling or diluting microliter quantities of regents, analytes or cells for bioassays and the like include a vessel having a plurality of troughs for supplying an array of pipettes to effect the transfer. The vessel is automatically indexable on a horizontal table to bring a selected trough into register with vertical movement of the pipette tips. The table is then indexed to bring the tips into alignment with a plurality of microtiter tray wells. In a preferred form the troughs are of different widths to supply differing quantities of liquid to the pipettes for transfer.