We measured the accuracy and precision of the new AVL 940 computerized microsample blood gas analyzer by using 40 40-μL samples of tonometered blood at each of three different levels of PO2 and PCO2. The observed accuracy (as defined by the mean difference from expected values at each level of PO2 and PCO2) was found to be acceptable according to national standards of accuracy as defined by the College of American Pathologists (CAP) and the American Thoracic Society (ATS) proficiency programs. The observed precision (as defined by the standard deviation for the 40 measurements at each level of PO2 and PCO2) was found to be comparable to reported precision in two proficiency-program reference laboratories. We conclude that the AVL 940 blood gas analyzer measures PO2 and PCO2 with acceptable accuracy and precision as defined by CAP and ATS standards.