We use the experimental method to compare second-price auctions to "verifiable" multilateral negotiations in which the sole buyer can credibly reveal to sellers the best price offer it currently holds. We find that transaction prices are lower in verifiable multilateral negotiations than in second-price auctions, despite the two institutions’ seeming equivalence. The difference occurs because low-cost sellers in the negotiations tend to submit initial offers that are less than the second-lowest cost. We also compare the two institutions to previously studied first-price auctions and multilateral negotiations with nonverifiable offers. Second-price auctions yield the highest prices, followed in order by verifiable negotiations, nonverifiable negotiations, and firstprice auctions.