The objective of this study was to compare two portable lactate analyzers for testing canine patients in a clinical setting with a previously accepted methodology for measuring plasma lactate. Between Jan 1, 2005 and Jun 1, 2006, all samples were analyzed using two different portable analyzers (devices A and B), and 86 of those samples were also analyzed by a reference laboratory (REF). The concordance correlation coefficient (CCC) for device A and the REF was 0.949 (95% confidence interval [95% CI], 0.923-0.966). For device B and REF, the CCC was 0.990 (95% CI, 0.985-0.993). Only 8 of 85 samples (9.4%) exceeded a relative difference of 20% for device B (note that 1 of the 86 samples was not included because the lactate level fell below the detectable limit of device B), but 48 of 85 samples (56.5%) exceeded a relative difference of 20% for device A. Both portable lactate analyzers appeared to be effective in detecting clinically significant elevations in plasma lactate compared with the REF but device B had better agreement. A positive correlation among all three analyzers existed; however, the analyzers do not yield directly interchangeable results.