The human zona binding test is the most predictive test of sperm function yet the availability of human zona severely restricts its clinical use. The primary aim of this study was to use a commercially available in-vitro transcription and translation system to produce immobilized recombinant human ZP3 (rhuZP3) on agarose beads. The biological activity of this preparation was examined using sperm binding and the acrosome reaction. Significantly higher levels of sperm binding to rhuZP3 beads (n = 12, P < 0.05) compared with controls were observed and there was a significant induction (n = 12, P < 0.01) in the acrosome reaction after overnight incubation at 37 degrees C in 5% CO2 in air. In conclusion, the in-vitro transcription and translation system can produce sufficient quantities of purified immobilized biologically active rhuZP3. These preliminary experiments will enable further refinements to be made so that a solid-phase sperm function test based on rhuZP3 coated beads is likely to be developed in the near future.