We investigate stock market rationality by examining the timeliness and unbiasedness of the market's response to dividend announcements.Our initial findings for market timeliness show a sluggish market reaction to dividend announcements; however, when the ex-dividend effect is controlled for, we find no evidence of a sluggish market reaction. We examine the unbiasedness of the market's response by testing whether the net announcement effect across a sample that is devoid of ex-post selection bias sums to zero. We observe a significant positive net announcement effect and examine several plausible conjectures for this puzzling phenomenon, but none provides a satisfactory explanation.