The principal goal of the EPA Environmental Monitoring Systems Laboratory (EMSL) in assessing the quality of measurements is the development of accurate standards that may be used by agency personnel (federal, state, and local) to audit and assess the quality of measurements. EMSL's development of ppb cylinder gas standards, containing hazardous organic compounds, was initiated to meet the need for audit materials to assess the quality of trial-burn-test measurements during hazardous waste incineration. The logic used in selecting organics for this standards development and the procedure used to ensure the highest possible accuracy in these standards are described. Also discussed is the apparent need for high quality gas standards for ambient air hazardous organic measurements and the extent to which the current inventory of 29 organic standards fulfills this need.