This article reviews commercially available instrumentation for inkjet printing of polymer micro-arrays for combinatorial materials research, and requirements thereof. These include a print head positioning accuracy better than 10 mum and a minimum drop volume of 100 pL. Commercially available instruments that fulfill these requirements can be divided into two categories, depending on whether they receive ink from a reservoir (dispense mode) or through fluid aspiration (pipette mode). Instruments belonging to the first category are restricted to the preparation of polymer blend micro-arrays. These consist of a few substances mixed in various ratios. The other instruments can be used for the preparation of both micro-arrays of large numbers of different pure polymer compounds and polymer blend micro-arrays. Moreover, ways to mix compounds are discussed.