The j-MOS transistor reported earlier has now been fabricated in silicon-on-insulator (SOI) prepared by oxygen ion implantation. Significant improvements in the drain breakdown voltage and off-state leakage current are attributed to a contoured gate oxide and to the quality of the SOI structure, respectively. The electron mobility in the channel silicon is 910 cm2/V . s and the minority-carrier lifetime is 3 µs. We conclude that the j-MOS transistor in SOI shows promise for controlling moderate power loads, particularly in dielectrically isolated power integrated circuit applications.