As a geographically integral part of south China, the population mix of Hong Kong is largely influenced by itslocation. In the past150 years, its population has increased from a fewthousand to 5.7 million. This is the resultof episodic influxes of a great mass of people from China, often associated with political upheavals or economic cri-sis. It explains a population structure of95% Chinese. This structure is also reflected in the finding of genetic vari-ants in this population, which bears resemblance to neighbouring regions in China. For example, the thalassaemiasand lactose intolerance are common. However, the impact of migration from other parts of China cannot be neglec-ted, particulary for the last half century. This is evident from studies of glucose-6-phosphate dehydrogenase(G6PD) variants and other protein polymorphisms. The quick change in political situation has also promoted moreinflux of people from central and northern part of China. They bring with them a diversity of genetic constituent,mutations and diseases. However, as an international city, Hong Kong has significantinputfrommostethnic groupsin the world. Hence, the remaining 5% of its population is a heterogeneous group of minorities including Europe-ans, Indians, Japanese, and south-east Asians. Although their contribution to the cultural and economic growth inHong Kong is phenomenal, their impact on the genetic load is small. However, since their genetic makeup, andhence diseases, vary somewhatfromsouthern Chinese, they also poses specific needs to the provision of clinical ge-netic services.