Previous studies have established that hydrogen sulphide and mercaptans are the primary components of halitosis (bad breath). In the present investigation, we report a simple, rapid technique for measurement of halitosis-related sulphides. The technique is based on a portable instrument generally used for environmental safety applications. Seventy-five volunteers were measured using this technique, and the results (in peak ppb hydrogen sulphide equivalents) compared with organoleptic assessment by 7 judges. A highly significant overall correlation (r = 0.603; P less than 0.001) was obtained between these 2 methods. Moreover, in most cases, the organoleptic ratings of the individual judges correlated more highly with sulphide monitor values than with one another. The simplicity of the technique suggests its use in clinical studies as well as in diagnosis and treatment of patients with this complaint.