The treatment of the upper extremities is not as prevalent as that of the lower limbs, but it is nonetheless equally important. Today, there are no load data relating to upper extremity bone-anchored prosthesis users in the literature, but they are important in order to improve the rehabilitation protocol, design aspects and confidence of the user when it comes to loading the prosthesis in daily life. The aim of the present study was to investigate, in a population of eleven transhumeral amputees with osseointegrated implants, the load levels reached during specific prosthetic movements at maximum voluntary effort and during daily activities. The data showed a wide range of maximum load levels throughout the different activities. Furthermore, the data indicate that some test subjects felt apprehensive about loading the prosthesis, resulting in relatively low loads compared with the group as a whole. Within the limits of the present study, it was concluded that loading the implant system was subject specific, which resulted in large subject-to-subject variability. Moreover, some subjects exhibited uncertainty about the levels that could damage the fixation or the implant system. The study illustrates the diversity and uncertainty that exist in a population of transhumeral amputees treated with bone-anchored prostheses in terms of loading in daily life.