Abstract: Apparatus for producing a plurality of arrays of reagent regions is disclosed. A dispensing assembly in the apparatus has a plurality of heads which are spaced for depositing reagents at selected positions in different array areas in a substrate. As the heads in the assembly are advanced along array area, the regions in a row in that array are successively filled, allowing parallel deposition in several array areas at reagent regions which are closely spaced relative to the spacing between deposition heads in the assembly. Also disclosed is a method for producing a plurality of arrays using the apparatus.