The ability to divide attention of persons who had sustained a severe Closed Head Injury 5 to 10 years before (chronic CHI patients), was examined in a dual-task experiment administered to 15 CHI patients and 34 control subjects. Both the patient group and the control group consisted of active licenced drivers at the time of the investigation. One task was a compensatory tracking task requiring lane tracking, a basic skill or car driving. The other task was a self-paced visual choice reaction time task. Single-task difficulty was individually adjusted by adaptive task procedures (on both tasks CHI patients reached significantly lower performance levels in single task conditions). With individual differences in single-task performance thus controlled, the ability to divide attention was found to be approximately equal in the chronic CHI patients and the control group. A surprising finding in this light, however, was the significant positive correlation between severity of injury (PTA duration) and divided attention costs in the patient group. © 1989, Masson Italia Periodici s.r.l. Milano. All rights reserved.