Exploratory drilling in the Four Corners--Intermountain area decreased slightly in 1978, with Utah having the greatest decline. The success rate also showed a decline from 18.9% in 1977 to 17.1% in 1978, but total footage drilled increased 5% in 1978. Development drilling increased 23% from 1977, with most of the activity centered in the San Juan basin of northwestern New Mexico, where the success rate remained at 94%. Development drilling remained active in the Aneth area, the Uinta basin, and the Overthrust belt in Utah. The most significant new-field discoveries were in Utah's Summit County in the Overthrust belt, where new fields were located. The largest oil and gas discoveries were from the Jurassic Nugget Sandstone and Twin Creek Limestone, respectively. The appare t discovery of Nevada's third oil field was completed at the close of 1978 in Nye County. The first of 6 offshore wildcats in Great Salt Lake was abandoned in basement rocks. Leasing and geophysical activities remained high in the Overthrust belt from Idaho to Arizona, and geophysical activity increased in the Paradox fold and fault belt in southeastern Utah and southwestern Colorado. Wildcat drilling activity is expected to increase in those areas. Development drilling should continue to be active in 1979.