This thesis is a summary of the following original papers: I. An epidemiological study of child health and nutrition in a northern Swedish county. I. Food consumption survey. Acta Paediat Scand, 60: Suppl. 214, 1971. II. An epidemiological study of child health and nutrition in a northern Swedish county. II. Methodological study of the recall technique. Nutr Metabol, 12: 321, 1970. III. An epidemiological study of child health and nutrition in a northern Swedish county. III. Medical and anthropometrical examinations. Acta Paediat Scand, 60, 1971. In press. IV. An epidemiological study of child health and nutrition in a northern Swedish county. IV. Haematological investigations, especially in regard to iron deficiency anaemia. Acta Paediat Scand, 60, 1971. In press. In collaboration with S. Sjölin. V. An epidemiological study of child health and nutrition in a northern Swedish county. V. Oral health studies. Odont. Rev, 22, 1971. In press. In collaboration with H. Grahnén and G. Lindström. VI. An epidemiological study of child health and nutrition in a northern Swedish county. VI. Relationship between general and oral health, food habits and socio-economic conditions. In collaboration with H. Grahnén and E. Arvidsson. To be published, 1971.