Hepatocyte　growth　factor　activator　inhibitor　1　(HAI-1)　is　a　multi-domain　membrane-associated　protease　inhibitor　that　potently　inhibits　a　variety　of　serine　proteases　such　as　hepatocyte　growth　factor　activator　and　matriptase.　Different　truncates　of　HAI-1　show　varying　potencies　for　inhibition　of　target　proteases,　suggesting　that　the　domain　organization　of　HAI-1　plays　a　critical　role　in　its　function.　Here,　the　soluble　full-length　extracellular　part　of　HAI-1　(sHAI-1)　was　expressed　using　the　Drosophila　S2　insect-cell　expression　system.　Diffraction-quality　crystals　of　sHAI-1　were　produced　using　ammonium　sulfate　as　precipitant.　The　crystal　diffracted　to　3.8　angstrom　resolution　and　belonged　to　space　group　P41212,　with　unit-cell　parameters　a　=　b　=　95.42,　c　=　124.50　angstrom.　The　asymmetric　unit　contains　one　sHAI-1　molecule.