The design and testing of Transcalent Solid State Power Devices are described. In a Transcalent Device the active element is made an integral part of two heat pipes. Thus the mechanical and thermal barriers between the silicon and the heat rejection surfaces are eliminated. Discussed will be the operational characteristics of the Transcalent Devices and, briefly, the design and fabrication of a 400 - ampere RMS Transcalent Thyristor, 250 - ampere Rectifier and design objectives of a high power transistor.