General Requirements:
Hong Kong carefully controls the arrival of immigrants in order to keep the population of immigrants within acceptable limits. Having successfully entered Hong Kong, the right to remain is guaranteed by the possession of a government-issued Smart ID card. These ID cards are used frequently in daily life and by law must be carried at all times by everyone over 11 years of age. Foreign residents are not exempt from police spot checks; while they are waiting for the issue of their ID card foreign residents should be prepared to provide proof of their identity on demand. This can be in the form of a current passport or the document which shows that application has been made for an ID card.
They must have a U.S. passport valid for at least six months and evidence of adequate funds for their stay and onward transportation. Those wishing to stay more than three months must obtain visas from a Chinese Embassy or Consulate. Visitors are not permitted to study or work (whether paid or not).
U.S. citizens may visit Hong Kong for up to 90 days without a visa, but a visa is required for those to work, study, establish or join in any business or to take up residence.