Continuous mental workload registration is a key technology for evaluating and optimizing work conditions in human-machine systems. Despite the urgent need for this technology, its technical measurement is still lacking. The long-term goal of this work is the establishment of precisely such an objective method. The article describes the development of a continuous method for neuronal mental workload registration during the execution of cognitive tasks. The sample consists of 54 people in paid work. The electroencephalogram as well as further workload relevant biosignal data and the NASA-TLX as a subjective questionnaire method are registered. Results from the workload classification of the EEG segments are presented. They are in concordance with the results expected from different task requirements on the executive functions. Findings from the subjective ratings, accuracy rates, and cardiovascular parameters underscore this fact.