The abnormal returns and volumes of a sample of junior resource companies who publicly released drill-core assay results are studied. Firms with favorable assay result announcements exhibited a liquid market for both event window panes, whereas firms with unfavorable assay result announcements exhibited a liquid market for the pre-and near-center part of the postannouncement panes of their event windows. Firms with favorable announcements exhibited statistically significant positive abnormal returns prior to (and during) the week of such announcements, and statistically significant negative abnormal returns after such announcements. Firms with unfavorable announcements exhibited statistically significant negative abnormal returns before and after such announcements. Participants who sold short into the abnormally high trading volumes prior to such announcements potentially would have earned abnormal returns by covering their short positions after the public announcements. However, the profitable realization of these identified large abnormal returns for a real-world trader can be expected to be severely constrained by the impact of bid-ask spreads, brokerage costs, and various institutional impediments (such as stringent short-sale regulations and the absence of “official” market makers).