The generation of hydrocarbons from dissolved organic matter appears to offer a solution to the long perplexing problem of introducing hydrocarbons into migrating water for transport to evolving oil fields. In this hypothesis two processes required for the formation of petroleum--generation and migration--are collapsed into a common process that overcomes fundamental problems surrounding mobilization of hydrocarbons from so-called source rocks. In the proposed hypothesis, hydrocarbons simply are generated from dissolved organic materials in the migrating water, are carried along in a molecularly dispersed form, and ultimately, in total or in part, are stripped from the migrating water to form oil fields. All essential elements of the processes of formation, transport, and accumulation now seem to be in place. Thus, conversions of humic substances at ambient temperatures are demonstrated. Alkanes--normal, branched, and cyclic--and aromatics are readily produced under laboratory simulations at temperatures as low as 130 C, sulfur compounds are generated under even milder conditions, and porphyrins are available in homologous form almost directly from microflora. Quantitatively, the rates and quantities appear to be in the right range for the development of major oil fields in basins of ordinary size.