The major justification for field analysis is the production of data and information that allows decisions to be made in a timely fashion for effective mitigation and/or efficient remediation of environmental contamination. Secondary benefits include lower cost per sample, more samples analyzed per work shift, and improved monitoring for worker safety. However, all of these applications require production of field analytical data of high quality and documented consistency and integrity. These data quality requirements place special constraints on the analytical instruments that are used for field analysis. The application and analytical capabilities of a dual silicon micro fabricated gas chromatographic instrument, with dedicated microprocessor control of all analytical functions, are discussed in relation to fieldable analytical chemistry. This small, rugged and very fast instrument provides for redundancy in analytical results, or, alternatively, the use of different modes of separation to achieve a wide variety of analytical capabilities within a portable instrument configuration.