What motivates manufacturing companies to make costly investments in producing in an environmentally clean manner? The traditional argument is that such behaviour is value reducing, and that therefore, firms must be forced by regulation to invest in "green" production processes. A counter-argument is that firms have an incentive to make environmental investments in an attempt to attract "green" consumers and investors, hence gaining competitive advantage over their rivals. In this paper, we employ a game-theoretic approach that demonstrates that competing firms' (...) incentives to make voluntary investments in environmental "clean-up" are affected by the size of the investment costs and the extent of consumer and investor "green" awareness. We argue that an increase in green behaviour can be induced by a combination of governmental subsidies for firms that invest in environmentally clean production processes, together with an education program that promotes "green" awareness amongst consumers, investors and the managers themselves. (shrink)