Six human volunteers were exposed to 10 and 20 ppm carbon disulfide at rest and to 3 and 10 ppm carbon disulfide under a 50 W level of physical exercise during four consecutive periods of 50 min. At the start of the experiments, at the end of the exposure periods and during the post-exposure period, urine was sampled and the concentration of 2-thiothiazolidine-4-carboxylic acid (TTCA) was determined. It was established that only a small percentage, ranging from 0.7 to 2.2% of the absorbed carbon sulfide was transformed into TTCA. The excretion rate of TTCA (mumol TTCA h-1) was found to be the best parameter in evaluating the respiratory uptake of carbon disulfide over a range of 37.9 to 163.3 mg CS2 compared to the urinary concentration of TTCA (mole TTCA ml-1) or the creatinine corrected concentration of TTCA (mmol TTCA mol-1 creatinine). The total amount of TTCA (mumol TTCA) excreted proved to be independent of the urinary flow (ml h-1), the estimates of the individual fatty tissue content and the urinary pH. No correlation was found between the respiratory uptake of carbon disulfide (mg CS2) and the excretion rate of TTCA within each exposure condition of 3, 10 or 20 ppm carbon disulfide, respectively.