Solenoid inkjet valves are characterized and implemented in an automated chemical microdispenser, the ChemJet, to be used for combinatorial library synthesis, A novel high-density format for chemical synthesis and assay is also presented, The ''ChemSheet'' consists of a 48x48 array of 8-mu L wells, molded as an 8(1/2)-in.x11-in. sheet of polypropylene. The development of the ChemSheet created the need for high-speed, parallel microdispensing. The ChemJet addresses this need by providing the ability to dispense 8-mu L volumes of chemical reagents to the 2304 wells of the ChemSheet in under 10 s, with an average reproducibility of similar to 2.2%. Results from both quantitative and qualitative characterization of inkjet solenoid valves are presented, Characterization of the ChemJet instrument is also presented.