The presence of organic material in potential source rocks significantly affects geophysical wireline responses. Inasmuch as the latter provide a continuous, complete, and readily available subsurface formation data record versus depth, many investigators have studied the possibility that organic carbon content and the source rock potential of subsurface strata can be identified from wireline logs. The present discussion reviews such log anomalies as observed by means of resistivity, acoustic, nuclear, natural gamma-ray spectral, and pulsed neutron measurements. The application of these well logs in open and/or cased wellbores as an indicator of the amount of organic matter contained in sediments is discussed and illustrated based on empirical correlations established with individual and/or combinations of several logging parameters. Fieldcase examples from several geographical areas are presented.