Sediments obtained from several environments of deposition were assayed for their potentiality as future source beds of petroleum, by the method of dry destructive distillation. Except for deposits from an algal lake that yielded 28 gallons of oil a ton, the maximum production was about 3 gallons a ton. As is true with rocks of past geologic formations, recent sediments regarded as good potential source beds are not plentiful. The majority of modern deposits gave little or no oil on distillation and the samples from only four major regions, Lake Maracaibo, Pamlico Sound, and the limestone-forming areas of Florida and Cuba, produced more than 2 gallons a ton. In order to aid the evaluation of the potentiality of modern sediments as source beds, several deposits from past g ologic formations were assayed in the same manner in which the recent sediments were treated. The results were strikingly similar to those from modern sediments, and support the view that the richer types of recent deposits are to be considered as potential future source beds. In general, the yield of oil from modern deposits increases as the texture becomes finer. This indicates that rocks formed from clay are more likely to be source beds than those made from silt or sand. The relatively high yield from the limy oozes of Florida and Cuba indicates that limestones may be mother rocks of oil. Deposits subject to considerable tidal action do not appear to be good future source beds. A suggestion is made that the organic content of sediments deposited relatively near shore is likely to be icher than that of those laid down far from land. If this is true it supplements other evidence pointing to the importance of shore-line conditions in the formation of oil. However, locally, the distribution of organic matter in sediments is influenced by the action of waves and currents, which may cause differences in the potentiality of sediments as source beds, even though the physical characters of the deposits may seem to be similar.