A total of 129 workers exposed to carbon disulphide (CS2) and 81 non-exposed controls were asked about their current use of pharmaceuticals, using a self-administered questionnaire. In all, 31% of the exposed and 19.8% of the non-exposed used some medicine (P = 0.08). The average number of pharmaceuticals per subject amounted to 0.71 in the exposed vs. 0.36 in the non-exposed (P = 0.049). Predominant types of medicines used were analgesics (12.4% in the exposed vs. 8.6% in the non-exposed, P = 0.50) and sedatives/hypnotics (10.1% in the exposed vs. 4.9% in the non-exposed, P = 0.21). The pharmaceuticals consumed can cause numerous (side) effects that are similar to the toxic effects of CS2. To take into account these possibly confounding agents, a classification system for possible (side) effects of pharmaceuticals was developed, taking the dose into account. According to this method, many (side) effects of pharmaceuticals that could occur were recorded with higher frequency and intensity in the exposed subjects. Potential (side) effects that occurred significantly more frequently in the exposed than in the non-exposed were: tiredness, sedation, dizziness (20.9% vs. 4.9%, P = 0.001), excitation, anxiety (10.9% vs. 2.5%, P = 0.03), vision disturbances (7.0% vs. 0%, P = 0.01), and erection decrease (5.4% vs. 0%, P = 0.045). The implications of these findings for epidemiological studies are discussed.