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The shuttle imaging radar C/X synthetic aperture radar (SIR‐C/X‐SAR) radar on board the space shuttle Endeavor imaged Kilauea Volcano, Hawaii, in April and October 1994 for the purpose of measuring active surface deformation by the methods of repeat‐pass differential radar interferometry. Observations at 24 cm (L band) and 5.6 cm (C band) wavelengths were reduced to interferograms showing apparent surface deformation over the 6‐month interval and over a succession of 1‐day intervals in October. A statistically significant local phase signature in the 6‐month interferogram is coincident with the Pu'u O'o lava vent. Interpreted as deformation, the signal implies centimeter‐scale deflation in an area several kilometers wide surrounding the vent. Peak deflation is roughly 14 cm if the deformation is purely vertical, centered southward of the Pu'u O'o caldera. Delays in the radar signal phase induced by …