The accuracy of the Halimeter, an inexpensive, simple instrument that measures total breath volatile sulfur compounds (VSCs), has not been adequately tested. We compared Halimeter measurements with those obtained with a specific and sensitive gas chromatographic (GC) technique. The Halimeter gave different, biexponential responses to a constant concentration of different VSCs: The relative response rate and sensitivity were hydrogen sulfide > methyl mercaptan > dimethylsulfide. The transient peak VSC concentration of oral samples was reached long before the sulfide detector fully responded. The GC measurement of initial total VSCs in breath samples was 2.7+/-0.48 times greater than the peak concentration of the Halimeter. However, the plateau phase measurement of the Halimeter was 25% greater than that of GC. While GC and Halimeter measurements positively correlated, appreciable differences were observed. In studies where relatively precise VSC measurements are required, GC is the preferable technique.