English summary: A random cross-sectional survey was conducted on 1263 children between 1 - 36 months of age in 9 communes of 6 provinces in the Northern mountainous areas, including Thai Nguyen, Ha Giang, Lang Son, Son La, Hoa Binh and Lai Chau, with the typical ethnic communities: San Diu, Mong, Tay, Thai, Giay, Muong, and Kinh from June 1994 to November 1996 in order to identify the prevalence of rickets in children.