Carbon disulphide (C 5 2 ), a reagent of rayon production, is known for its high toxic potential and has therefore been the subject of many clinical studies The aims of the study presented here were to determine the effective exposure to C 5 2 and to compare the validity of the different exposure indicators Internal and external exposure to C 5 2 was investigated in 362 male workers of a viscose factory The C 5 2 air concentrations measured through stationary air monitoring in five different work areas (n = 39) were compared with the values of active personal air monitoring (n = 51) and passive personal air monitoring (n = 352) In addition, in all investigations biological monitoring was carried out by measuring the 2thio-1,3-thiazolidine-carboxylic acid (TTCA) excretion in urine A significant correlation was found between the data for active and passive personal air sampling (y = 0.99, x + 0 31, r = 0 968) The results of the stationary measurements led, however, to values which were systematically too low The validity of TTCA excretion in urine as a parameter of biological monitoring could for the first time be verified in a large sample of subjects There was a linear correlation between TTCA values in the urine related to both volume and creatinine ly (TTC Amg/g creatinine) = 0 315 x (ml C 5 2 /m 3 air) + 0 59 l and the C 5 2 values in the air Nevertheless, TTCA excretion proved to be dependent upon creatinine so that the excreted amounts related to creatinine described the individual exposure more exactly.