This Application Note describes the extraction and determination of oil and grease from waste water samples following Standard Methods 5520 part D (Soxhlet Extraction Method). “Oil and grease” is defined as any material recovered as a substance soluble in the solvent. Therefore, compounds with similar physical properties will be determined as well as oil and grease (e.g.sulfur compounds, organic dyes, chlorophyll). The waste water sample is acidified with hydrochloric acid and extracted using a Soxhlet extraction method on the Extraction Unit E-816 SOX. After the extract has been dried to a constant weight, the amount of oil and grease is determined gravimetrically. This Application Note is suitable for biological lipids and mineral hydrocarbons, as well as for most industrial waste water. It is not applicable to low-boiling point fractions which vaporize below 85 °C. For this Application Note distilled water spiked with a unflower seed oil (certified reference material) was used. A blank was determined as well.