Invited Commentary on Dr. Isaac Kaplan's Paper "Age Dating of Environmental Organic Residues".

Comments on the paper "Age Dating of Environmental Organic Residues," by Isaac Kaplan. Focus of the commentary on the petroleum fuels of organic materials; Recognition of the factors considered during age dating of petroleum releases; Importance of establishing a constituent in the fuel; Development of ratios of dateable constituents relating to fuel constituents; Proposal to estimate age in gasoline contaminated groundwater; Discussion of the nC17/ pristane ratio for age dating diesel fuels and the T8 ratio for dating regular and mid-grade gasolines.