The number 8 is considered lucky under the Chinese culture. This paper tries to examine whether investors hold such superstitious belief in the Hong Kong Stock Exchange. Using the transaction level data, we first show that more intense net buying occurs at 8-ending lots. Next, we seek favorable evidence in support of financial complexity hypothesis and informed trading hypothesis, both of which are effective in expounding the prevalence of this biased trading behavior. Finally, we find that traders’ learning by means of information acquisition is able to alleviate the lucky-8 effect on superstitious traders.