a b s t r a c tUsing cross-country data on trading by international mutual funds, I find that firms with more opaque information environments, as captured by firm-and country-level measures of the availability of financial reporting information, experience more privately informed trading by institutional investors. The association between firmlevel opacity and informed trading is most pronounced where country-level disclosure infrastructures are less developed and for those investors for whom the incentives and opportunities to acquire private information are greatest. A difference-in-differences analysis of the returns earned by institutions in opaque stocks suggests that this information advantage is economically significant.