The efficacy of aids to individual decision making has received little or no attention in published psychological literature. A number of untested assertions have been made in recent years concerning the usefulness of training in decomposition techniques as an aid to decision makers. This study examined the effects of such training on groups of managers and senior professional staff in two large organisations. It was expected that subjects trained in a systematic procedure for decomposing decisions would report a more structured approach to information processing in their decision making. Discriminant analysis of six principal factors identified from responses to a Decision Making Questionnaire failed to identify significant differences between trained and untrained subjects. Trained subjects expressed more dissatisfaction with lack of goal clarity in organisational settings. The principal benefit of training was reported as an aid to communication in decision making groups. It was expected that differences would be found between organisations; as one organisation had "institutionalized" such training programs over some years. No significant differences were found between organisations on any of the six factors. 27 trained subjects of both sexes were matched with 27 untrained subjects. Additional data was collected from interviews with each subject. It was concluded that, at their present stage of development, normative theories of decision behaviour do not account for a sufficiently large proportion of variance to be useful as aids to individual judgment and decision making. It was conjectured that social learning theory provides a more useful model of decision behaviour in organisations.