This study attempted to identify, in a mixed group of chronic patients, a specific measure of cognitive processing that may be of use in predicting dependence on psychiatric care. The measures investigated are derived from reaction-time tasks. Difficulties of response processing seem to account for the largest amount of variance in current service use. When compared with other variables shown to have some predictive power (e.g. social behaviour, symptoms and chronicity), the reaction time measures fare well. Functions derived from discriminant analyses using all the variables correctly classified 90% of those requiring day care and 95% of those requiring night care. Stepwise methods produced lower classification rates but always included reaction-time measures in the predictor set. Patients with continuing cognitive difficulties are likely to remain in more supportive psychiatric settings despite rigorous rehabilitation procedures.