In this paper, we conjecture that the weak association between disclosure and cost of equity capital found in the literature (Botosan, 1997) can be caused by the high-level corporate disclosure environment found in the United States. We hypothesize that in low-level corporate disclosure environments the variability in disclosure practices across firms will be larger than in the United States, and, consequently, the marginal effect of voluntary disclosure policies will be higher. Using a newly developed Brazilian Corporate Disclosure Index (BCDI), our results confirm this hypothesis. Disclosure is strongly associated with ex ante cost of equity capital for Brazilian firms. The results are more pronounced for firms with less analyst coverage and low ownership concentration, as expected.