Three main series of bound steroidal acids have been tentatively identified, in low concentrations, in the hydrolysates of kerogens and the extractable polar fractions of sediments from the Nordlinger Ries (southern Germany), and in a kerogen sample from the Monterey Formation (California). The results provide further evidence of the widespread occurrence of 3-carboxysteroids and indicate that they are chemically bonded to the complex network of kerogen through ester linkages. This suggests that these compounds could represent a yet unrecognized family of compounds occurring in the biosphere.