The study reported in this book provides descriptive material about a national sample of illegitimate children born in Great Britain in 1958. It compares their development with legitimate children who were born in the same week as they were, and it relates their development, at the age of seven years, to a range of factors linked with their birth history as well as with their mothers' social and personal background. Part I provides a brief review of the most relevant major studies carried out previously. Part II looks at the mothers' circumstances before and during pregnancy, as well as at the conditions which prevailed at birth and during the first month of the child's life. In Part III, the children's development at the age of seven years is described and compared with that of their peers. Part IV provides an overview and some suggestions for the future. The appendix contains statistics and a description of the sample and its identification, notes and statistical tests for the main text tables, and tables not included in the text. (Author/SB)