This paper describes the prevalence of behaviour problems in 2 populations of preschool children in London, and the continuities over time of common problems. Night waking was the most common problem under the age of 2, being reported in 21% of 1-year-olds. Just under half of these night wakers were still waking at 18 months, and from 18 months to 2 years just over half the children continued waking The continuities of feeding problems were stronger after the age of 2 years, with poor appetite being reported to persist more than food fads. Over 2 years the most common problem reported was temper tantrums, and 45% of the children having frequent tantrums at 2 years were still having frequent tantrums at 3 years. The implications for services and the need for intervention studies are discussed.