The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has evaluated the possibility to add the indication “prerequisite for Pregnancy Risk Group C” to the classification of Pregnancy Risk Group B for dimethyl sulfoxide at the maximum concentration at the workplace (MAK value) of 50 ml/m3. The lowest NOAEL for developmental toxicity in rabbits is 300 mg/kg body weight/day, which after toxicokinetic scaling corresponds to a concentration of 268 ml/m3 at the workplace. Liquid dimethyl sulfoxide penetrates the skin at the same rate as dimethylformamide. In addition to the amount taken up via the lung, it has to be assumed that the same amount of dimethyl sulfoxide is taken up via the skin from the gas phase as was shown with dimethylformamide in volunteers. Therefore, damage to the embryo or foetus is unlikely at the concentration of 12 ml/m3 and less. An exposure not higher than this concentration would be the prerequisite for an assignment to Pregnancy Risk Group C.