Bis(2-ethylhexyl) phthalate (DEHP) is classified as a "priority hazardous substance" by the European Union, a probable human carcinogen by the United States Environmental Protection Agency, and is a suspect human endocrine disruptor. This ubiquitous compound is measurable in many food matrices. Screening of nine fatty and processed foods commonly consumed in the United States for DEHP was performed with an internal standard addition method that utilized Gas Chromatography-Electron Impact Mass Spectrometry (GC-EIMS). Blank-adjusted average mass fractions in each food ranged from 0.18 mg/kg (± 0.07 mg/kg, 1 σ) to 1.57 mg/kg ( ± 0.24 mg/kg, 1σ), with cheeses containing the largest. Organisms such as penicillium used in the production of Stilton cheese have been considered likely sources of naturally-occurring phthalate. While Anthropogenic DEHP is produced from petrogenic chemicals, biogenic DEHP is likely produced by organisms utilizing atmosphere-equilibrated carbon containing a quantity of 14C isotopes measurable by Accelerator Mass Spectrometry (AMS). The 14C abundance of DEHP isolated from Stilton cheese allowed for the determination of its contemporary, and thus biogenic, fraction of carbon. Five ∼ 90 µg quantities of DEHP were extracted from ∼ 12 kg of cheese and isolated by silica gel, size exclusion, and high performance liquid chromatography (HPLC) for AMS. Sample masses were determined by GC-EIMS and combusted CO₂ manometric measurements. The purity of carbon as DEHP in each isolate (87.2 % ± 1.7 % to 94.0 % ± 1.3 %, n=5, 95 % C.I.) was determined by multivariate deconvolution of GC-EIMS fragmentation spectra. Concurrently processed isolation method blanks contained from 0.61 µg ± 0.04 µg to 1.84 µg ± 0.09 µg (n=3, 1 σ uncertainty) DEHP per sample and significant quantities of extraneous carbon contamination. Measurements of 13C/12C isotope ratios were made to correct reported 14C values for instrumental and natural fractionation. The mean 14C-corrected contemporary carbon fraction of DEHP in all isolates was 0.242 ± 0.068 (n=5, 1 σ uncertainty), revealing that the majority of DEHP in Stilton cheese, at 75.8 % ± 6.8 %, is anthropogenic, but with a significant naturally-occurring component.