In order to make Bureau of Mines analyses of crude oils more useful, the value of including a determination of nitrogen content was investigated. Nitrogen contents of 153 crude petroleums from all parts of the United States were investigated. In general, the more asphaltic crude oils contained the higher nitrogen contents and the bulk of the nitrogen was in the high molecular weight portion of the oils. Correlations were developed between the Conradson carbon residue of the oil and the nitrogen content for oils from particular geological periods. The nitrogen content of petroleum fractions is assuming considerable importance because of its adverse effect on cracking catalysts and on stability of finished products. Consequently, generalizations as to the amount of nitrogen in the crude oil and information as to its boiling-range distribution are important in the selection of crude stock for particular operations. Correlations of nitrogen content with geologic age may give clues as to the origin and process of conversion of petroleum.