The overall objective of the two-phase MWD project was to develop a mudpulse MWD tool that could be used where downhole temperatures are as high as 195?C (383?F). Phase I objectives were to: (1) identify components of existing systems that cannot operate at 195?C; (2) locate high-temperature replacements or develop new designs, (3) develop a cooling technology to keep components at acceptable operating temperatures; (4) test new designs and components under high temperatures in the laboratory; and (5) assemble two high-temperature MWD prototype tools and test each in at least one low-temperature well to verify total system performance.