Protein arrays will greatly accelerate research and development in medical and biological sciences. We have used cell-free protein biosynthesis and a parallel immobilization strategy for producing protein biochips. We demonstrate a model two-protein microarray using luciferase and green fluorescent protein, both expressed in a cell-free system and specifically immobilized on CombiMatrix semiconductor oligonucleotide microarrays. This demonstration provides evidence for the appropriate folding, activity, robust presentation, and efficient flexible detection of proteins on the microscale.