ABSTRACTTwo infrared (IR) breath alcohol analyzers, the Alcotest® 7110 and the Intoxilyzer® 5000C, were evaluated against blood results and against the Breathalyzer® 900A currently used by Canadian police agencies. A total of 18 healthy human subjects were used for the breath to breath comparisons while 15 of those subjects each provided two blood samples approximately one hour apart for blood I breath correlations. The IR analyzers and the Breathalyzer® showed a high degree of correlation with blood samples (n = 15: r = 0.974 for the Breathalyzer®, r = 0.971 for the Intoxilyzer®, and r = 0.989 for the Alcotest®). All three Instruments underestimated the blood results (mean differences, blood minus breath: 12 mg% for the Breathalyzer®, 18 mg% for the Intoxilyzer®, and 9 mg% for the Alcotest®). In breath to breath comparisons the Intoxilyzer® underestimated the Breathalyzer® (n = 18, mean difference Breathalyzer® minus Intoxilyzer® = 4 mg%) while the Alcotest® overestimated the Breathalyzer® (n = 17, mean ...