An experimental study of the breakup of a liquid jet normal to a high-speed airstream is reported. The measurement techniques were laser-sheet tomography, to show the details of the breakup processes, and the Fraunhofer technique. The injectant used was water including fluorescent dye, Eosine-Y, and the light source which illuminated the spray was a Nd:YAG laser(532nm wavelength, 20ns pulse width) in the laser-sheet tomography. The important result obtained is that there are at least two types of atomization mechanisms. In the first mechanism, a horizontal section of the liquid column is distorted into a bow shape, and a cavity without drops exists behind the liquid column. Small drops are produced at both tips of the bow. The continuous length and the width of the liquid column were measured from the tomograms. In the second mechanism, in which velocities of both the airstream and the injecting water are low, the liquid column is distorted into a snakelike shape and drops are produced near the end of the liquid column.