Seven hundred twenty-six wells were drilled in Mexico during 1961, as compared with 762 drilled during 1960, for a total footage of 5,279,674 ft. or an average of 7272 ft. per well. Of the total number of wells drilled, 160 wells were classified as exploratory holes of which 94 were new-field wildcats, resulting in the discovery of 8 new oil and (or) gas fields. Other exploratory holes were classified as follows: 28 new-pool wildcats, 8 deeper-pool tests, 8 shallower-pool tests, and 22 outpost wells. Forty of these were completed as producers. Of the total of 726 wells drilled, 511 were successful. The new-field discoveries were located as follows: 2 gas productive in the Eocene trend of northeastern Mexico; 4 new oil fields in Cretaceous formations and one small gas field in Eocene formations within the Tampico embayment; and one gas field in Miocene formations in the Tabasco region. Surface geology and geophysical exploration activities were concentrated as in previous years along the coastal plain of the Gulf of Mexico. Increased exploration was also carried out along the Cretaceous trends in northeastern Mexico in the State of Coahuila; systematic gravity-meter surveys were continued in N.-central Chihuahua and in the Yucatan Peninsula.