Three groups of 10 male Sprague-Dawley rats were exposed daily, 5 days a week for 25 weeks, either to 500 ppm carbon disulfide (CS2), 50 ppm hydrogen sulfide (H2S), or to both of them as a mixture and were periodically examined for sensory and motor tail nerve conduction velocity (SNCV, MNCV). A concomitant control group of 10 rats was used. In addition, rats exposed to 500 ppm CS2, and those simultaneously exposed to 500 ppm CS2 and 50 ppm H2S, were twice examined for 24-h urine excretion of 2-thio-thiazolidine-4-carboxylic acid (TTCA) in the course of the experimental period. Simultaneous exposure to CS2 and H2S had no significant interactive effect on nerve conduction velocities. A significant time-dependent slowing down of MNCV and SNCV occurred as the result of chronic exposure to CS2, including exposure to 500 ppm CS2 and to the mixture of 500 ppm CS2 and 50 ppm H2S, but did not occur after chronic exposure to 50 ppm H2S. With combined exposure to 500 ppm CS2 and 50 ppm H2S, the quantity of TTCA excreted in 24-h urine was not significantly different from that occurring in response to CS2 exposure alone. On the basis of these results it is suggested that chronic exposure to H2S would neither influence CS2-induced peripheral nerve toxicity nor obscure the interpretation of the measurement of urinary TTCA as a biological indicator of CS2 exposure.