The present study is a part of a prospective, longitudinal investigation of caries development in children (n = 692) living in the southern suburbs of Stockholm. The aim was to evaluate, longitudinally, the caries-predictive ability of variables describing social and immigrant background, dietary habits, microbial and oral hygiene factors, and fluoride exposure in children at 1 and 2.5 years of age with respect to caries development before the age of 3.5. The predictors for caries development in children before 2.5 years of age were mutans streptococci (p