To what extent can private-sector bioprospecting incentives be relied upon for the protection of biological diversity? The literature contains dramatically different estimates of these incentives, from trivial to quite large. We resolve this controversy by isolating the fundamental source of the discrepancy and then providing empirically defensible estimates based on that analysis. Results demonstrate that the bioprospecting incentive is unlikely to generate much private-sector conservation. Thus, other mechanisms are likely required to preserve the public good of biodiversity.