Drilling of geothermal exploration and development wells showed a slight increase over 1980. In 1981, 99 wells accounted for 674,781 ft of hole. A total of 203,673 ft of hole was cut during the drilling of 37 geothermal exploratory wells. California again had the largest number of wildcats at 16, followed by Nevada with 10. Of the 62 geothermal development wells in 1981, representing 471,108 ft of hole, 56 were considered capable of production. The development success rate of 90.32% is slightly below the 1980 success rate of 94.83%. Also, there has been a significant increase in average depth, from 5,997 ft in 1980 to 7,901 ft in 1981. This seems to indicate that operators are having to drill deeper in their efforts to extend productive limits of proven geothermal reservoirs. Although there have been no new geothermal electrical power plants brought on-line in The Geysers during 1981, construction continued on 6 plants. Two small facilities, 1 of 3 MWe at the Puna District in Hawaii and 1 of 1.6 MWe at the Roosevelt Hot Springs KGRA in Utah, became operational in 1981. Movement toward smaller, semiportable, less expensive power plants.--Modified journal abstract.