The Cao Lan are officially considered part of the Zhuang nationality in China. They speak a distinct language - different from other Zhuang varieties - and possess their own set of customs and traditions.
Cao Lan is part of the Central Tai linguistic family. "The Cao Lan, a Sinicized group, consists mainly in various areas of the delta of northern Vietnam; it is also found in smaller numbers in China." It is possible that the Cao Lan language in China is what linguists label the Yan-Guang dialect of Southern Zhuang.
The Cao Lan in Vietnam migrated from southern China in the first half of the nineteenth century. Cao Lan communities are divided into various family lineages, each clan having their own peculiar customs and their own protective spirit. The Nung and Cao Lan joined with a powerful Hmong army in northern Vietnam in the 1860s. They took possession of large tracts of land and raided Buddhist temples of their gold. The Cao Lan were deceived into following Sioung - the charismatic, self-proclaimed Hmong king.
Strict morality codes are practiced among the rural Cao Lan. Women must observe strict rules and customs. Whenever a woman encounters a man in a social position superior to her husband's, she is required to hide behind bamboo. The Cao Lan were traditionally buried when they died but, due to a lack of land, the government has recently begun demanding that the dead be cremated instead. Traditionally, when the body was placed in the coffin, seven coins were added for a man and nine for a woman. The coins represent the Khue star which they believe guides the person's soul to his or her ancestors in the other world.
Spirit worship takes a major place in the lives of the Cao Lan population. Each branch of the nationality worships a different spirit such as the spirit of the river, the trees, the crops, etc. Elaborate festivals include the playing of castanets, copper bells, drums, cymbals, and wind instruments.
In China, as well as in Vietnam, the Cao Lan are unreached with the gospel, although 26 families in Vietnam came to Christ in 1999. Very few have had any exposure to the Christian message and the name of Christ remains unknown. Northern Vietnam and southern China have been Communist strongholds for three generations. No Christian ministries or Western mission organizations are known to be focusing on them.