California’s Proposition 65, The Safe Drinking Water Act of 1986 a voter-passed initiative, possesses some unusual information-generation and use features, together with some burdens of proof not usually seen in typical postmarket statutes. After placing Proposition 65 in context of other kinds of statutes, this paper describes the features of Proposition 65 and then analyzes what contributes to its efficacy as an environmental health statute. I argue that Proposition 65 has a number of characteristics that make it reasonably effective in reducing exposures to toxicants: its automatic provisions, the shifting of the burden of proof to firms that expose the public to toxicants, its meaningful sanctions, its “responsibility” attribute and its adaptability to address new toxicants.