The thesis presents some of the work carried out as part of the research and development programme for the provision of practical artificial upper limbs for a group of congenital amputee patients. The account commences by reviewing, in Volume 1, the problems presented by this population of amputees in the context of an ongoing limb fitting servicep and shows hoer the difficulties of prehension arise in this situation. The provision of upper limb prostheses in general is then reviewed with reference to representative literature on the subject, where various inadequacies of existing systems are considered in the context of the imsdiate practical problem of the provision of adequate prehension facilities for bilateral amputees. The experimental and practical work of Volume 2 commences with an appraisal of the requirements for a hand prosthesis in the light of the information derived from Volume Is, and this, together with the results of some simple experiments, leads to a broad specification for a hand mechanism. Various experimental mechanisms are then desoribed, leading to the development of a mechanism suitable for patient trials. The problem of the provision of the cosmetic cover for the meckanism emerges as the major obstacle in the way of further progress, and a new process for cosmetic glove production is devised, This is followed by consideration of the various problems of control associated with the hand prosthesis, some working hardware is developed and guidelines for future work on control are outlined. The thesis concludes with an appraisal of the work following trial fittings on patients, which shows the principles to be successful in Operation and indications for future trends are given