In October 1904 an article was published titled ‘Jobshop planning’, describing a rather simple but. effective manual system. From that time onwards quite a number of workshops within Philips have adopted production control systems based on these principles. The jobshops meant here manufacture spare parts, complete machinery and fine mechanical tools in small series, or single items on customer orders; 40 to 150 craftsmen were employed in each of them. What we wanted to achieve was short and reliable delivery times and a high utilization of production capacity. In ten of these jobshops, operating the system for periods of one to four years, the performances were inventorized. However, the fair results achieved seemed to be in contradiction to theoretical studies made at the same time, Therefore in addition to the survey an investigation was made as to why these differences occurred.