In a recent contribution to this JOURNAL, Donaldson and Eaton (1976) present an interesting and original analysis of the time profile of wages as a decision variable for firms investing in the specific training of their workers. The authors relate the profit-maximizing wage profile to two important sources of posttraining uncertainty: product prices and worker quits. This analysis can be extended to uncertainty arising during the training period itself. Here the most important source of uncertainty is the worker's training potential, and the most reasonable assumption is that this uncertainty is shared by worker and employer, both learning of the worker's abilities as he progresses through the formal and informal training programs of the firm. How does this uncertainty affect wage profiles? Following Donaldson and Eaton, let us assume that mobility of labour and profit-maximizing behaviour of employers require that workers be offered the same present value of lifetime wages in all employments, both in firms that do not train and in firms that do train. (In the latter, expected present value takes account of the probability of failing the training program.) This equality of present value leaves the time profile of wages as a decision variable for the firm. Uncertainty about workers' abilities influences the wage profile, first, because it introduces the possibility of self-screening by failing trainees, and secondly, because successful completion of training provides general information about the worker which raises his productivity in all firms. Although post-training quits are costly for the firm, quits during training can be cost-reducing if they represent self-screening by trainees who would otherwise fail the training program. At the beginning of the program the worker's training potential is unknown. On the basis of previous experience, worker and employer know the probability of success for trainees as a group, but knowledge about the performance of the individual trainee becomes available only as training proceeds, and may become available first to the worker. The time profile of wages can be used by the firm to encourage self-screening. If the wage received by the trainee is equal to that in alternative employment, the trainee has no financial incentive to quit. But if the wage is below that available elsewhere, the trainee has such an incentive as soon as he is aware that his