Abstract The pioneering longitudinal studies of child development (all launched in the 1920s and 1930s) were extended well beyond childhood. Indeed, they eventually followed their young study members up to the middle years and later life. In doing so, they generated issues that could not be addressed satisfactorily by available theories. These include the recognition that individual lives are influenced by their ever-changing historical context, that the study of human lives calls for new ways of thinking about their pattern and dynamic, and that concepts of human development should apply to processes across the life span. Life course theory has evolved since the 1960s through programmatic efforts to address such issues.