Abstract: The new neutron-deficient americium isotope 233Am produced via the 233U( 6Li, 6n) reaction has been identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport system. The -decay of 233Am and its subsequent -decay chain have been observed in the mass-233 fraction. The half-life and -particle energy of 233Am have been determined to be 3.20.8 min and 678017 keV, respectively. From these results and a deduced -decay branching ratio, the observed -decay is regarded as a favored transition.