A traceability procedure has been established which allows specialty gas producers to prepare gaseous pollutant Certified Reference Materials (CRM's). The accuracy, stability and homogeneity of the CRM's approach those of NBS Standard Reference Materials (SRM's). As of October 1986, 36 candidate batches had been audited. In general, the agreement between the producer's analytical results and the audit results have been within + or - 0.5% relative. Additional data suggest that CRM's are stable during their two-year certification periods. The purchaser of a CRM is assured that its accuracy is high because of four features of the CRM program: (1) The general technical procedure for producing and analyzing CRM's has been specified by NBS; (2) CRM's are directly traceable to SRM's which are used as reference standards during the analysis of CRM's; (3) The producer's analytical results are verified by measurements which are performed by an independent auditor; and (4) Both the producer's and the auditor's analytical results must be reviewed and approved by NBS before the CRM's may be sold.