A two-color multiphoton ionization spectroscopy of Zr has been performed using an atomic beam and pulsed dye lasers in conjunction with the use of a time-of-flight mass spectrometer. Zr atoms were excited from the ground state [4d 2 5s 2 ( 3 F 2 )] to the 17430 cm À1 state [4d 2 5s5p( 3 D 1 )] by one dye laser, and subsequently ionized by another dye laser. From the experiment, a total of 124 peaks originating from the 17430 cm À1 state were observed in the 565 -593 and 610 -652 nm regions. In addition 68 single-color multiphoton ionization peaks were observed. From the results of the ion mass analysis, isotopic selectivities between odd and even isotopes were observed at six ionization peaks. This suggests the existence of