Abstract: A system for producing a library of oligomer comprising at least two monomers in a positionally determined array comprise a plurality of synthesis supports, a first plurality of support carriers wherein each carrier has a uniform array of distinct support holding positions for the synthesis supports; means for contacting each array of synthesis supports with a different monomer to provide a first chemical transformation of the synthesis supports; a second plurality of support carriers wherein each carrier has a uniform array of distinct support holding positions for receiving the chemically transformed synthesis supports contained in the first plurality of support carriers; transfer apparatus for transferring a selected row or column of synthesis supports from each of the first plurality of carriers to each of the second plurality of carriers to enable the supports in the second to undergo at least a second chemical transformation; and whereby each support position in each carrier identifies the chemical comp