A highly unsaturated, sulfur-rich, naphthenic condensate was discovered in association with dry biogenic gas in the upper Tertiary of the southeastern Mediterranean coastal plain of Israel. Geologic and geochemical evidence suggests that this condensate was generated in thermally immature rocks. Similar material has been reported from the upper Tertiary of the western Mediterranean. We suggest that the immature condensates were formed from resin-rich, terrestrially derived organic matter. Under an equivalent thermal regime, marine material derived primarily from algae and bacteria will produce heavy crude, rich in asphaltenes.