Environmental data quality improvement continues to focus on analytical laboratoryperformance with little, if any, attention given to improving the performance of field consultants responsible for sample collection. Many environmental professionals often assume that the primary opportunity for data error lies within the activities conducted by the laboratory. Experience in the evaluation of environmental data and project-wide quality assurance programs indicates that an often-ignored factor affecting environmental data quality is the manner in which a sample is acquired and handled in the field. If a sample is not properly collected, preserved, stored, and transported in the field, even the best laboratory practices and analytical methods cannot deliver accurate and reliable data (i.e., bad data in equals bad data out). Poor quality environmental data may result in inappropriate decisions regarding site characterization and remedial action. Field auditing is becoming an often-employed technique for examining the performance of the environmental sampling field team and how their performance may affect data quality. The field audits typically focus on: (1) verifying that field consultants adhere to project control documents (e.g., Work Plans and Standard Operating Procedures [SOPs]) during field operations; (2) providing third-party independent assurance that field procedures, quality assurance/ quality control (QA/QC)protocol, and field documentation are sufficient to produce data of satisfactory quality; (3) providing a defense in the event that field procedures are called into question; and (4) identifying ways to reduce sampling costs. Field audits are typically most effective when performed on a surprise basis; that is, the sampling contractor may be aware that a field audit will be conducted during some phase of sampling activities but is not informed of the specific day(s) that the audit will be conducted. The audit also should be conducted early on in the sampling program such that deficiencies noted during the audit can be addressed before the majority of field activities have been completed. A second audit should be performed as a follow-up to confirm that the recommended changes have been implemented. A field auditor is assigned to the project by matching, as closely as possible, the auditor's experience with the type of field activities being conducted. The auditor uses a project-specific field audit checklist developed from key information contained in project control documents. Completion of the extensive audit checklist during the audit focuses the auditor on evaluating each aspect of field activities being performed. Rather than examine field team performance after sampling, a field auditor can do so while the samples are being collected and can apply real-time corrective action as appropriate. As a result of field audits, responsible parties often observe vast improvements in their consultant's field procedures and, consequently, receive more reliable and representative field data at a lower cost. The cost savings and improved data quality that result from properly completed field audits make the field auditing process both cost-effective and functional.