The report is an update of the exploratory report acrolein (Slooff et al., 1991) that served as a basis for the discussion during the exploratory meeting on acrolein in March 1992. The meeting supported the conclusion that priority should be given to the compartment air and to the risks to humans. With respect to inhalation and dietary exposure of humans to acrolein, a maximum permissible concentration of 0.5 mug.m-3 and a tolerable daily intake of 0.5 mug.kg-1 bw. day-1 (equivalent to 30 mug.day-1 for a 60 kg person) has been derived, respectively. The available data on human exposure levels indicate that the current acrolein concentrations in outdoor air (incase of high traffic density) and, especially, in indoor air likely exceed the maximum permissible concentration in air and that the dietary intake of acrolein may exceed the tolerable daily intake. It is noted, however, that with respect to the Netherlands only very limited data on acrolein concentrations in outdoor air are available and that data on acrolein concentrations in indoor air and in foodstuffs and beverages are lacking. Therefor, a sound risk evaluation is not possible.