The main task for the European Network on Longitudinal Studies on Individual Development (ENLS), initiated in 1985 under the auspices of the European Science Foundation, has been to discuss appropriate models for a developmental perspective on individual functioning in all its aspects and to analyse and discuss the consequences of such models for the application of a longitudinal design for research on this issue.

The history of systematically planned and performed studies of individual development dates back to the 1920s. One of the best-known longitudinal studies was implemented by Terman and his associates at Stanford in 1921 and followed the development of more than 1500 gifted individuals from early school years through adult life. The reports from this project cover a period of more than 50 years (see e.g. Sears, 1977). Two longitudinal studies initiated in 1928, the Berkeley Growth Study led by Nancy Bailey and the Guidance Study led by Jean W. Macfarlane, both implemented at the Institute of Human Development at Berkeley, and the Oakland Growth Study (the Adolescent Growth Study) initiated by Harold E. Jones and Herbert Stoltz in 1931, were pioneering works with the general purpose of studying a broad range of biological, behavioural, cognitive, motivational, emotional and social aspects of individual functioning. In spite of the fact that these studies were theoretically and methodologically well planned and carried out and also were concerned with central developmental issues, they did not stimulate many other researchers to follow. For a long time only a few well-planned studies appeared on the scene. During the last decades the initiation of longitudinal studies has increased, particularly in Europe.