All eligible study members were contacted.
| Provided information | tbc |
| Cumulative total of deaths | tbc |
| Cumulative permanent refusals | tbc |
| Temporarily living abroad | tbc |
| Cumulative Emigrated | tbc |
| Failure to contact | tbc |
Postal questionnaires were sent to school or college attended to ask administrators about courses taken by cohort members.
For cohort members who were no longer in education, postal questionnaires were sent to Youth Employment Service officers to complete from records or other sources about vocational guidance given and training and other courses attended.
Members of the control study population were sent postal questionnaires about employment and courses attended.
The control sample comprised a third of single births excluded by the initial sampling procedure, and all with fathers in manual employment (N=approx 2000).
Instructions are given at the head of each form.