Purpose – The purpose of the thesis is to improve picking operations that kit materials to assembly lines and based on that, develop a model concerning work balancing in relation to varying demand. To achieve this purpose the following questions of issue are answered: 1. What difficulties can exist in picking operations that kit materials to assembly lines? 2. How can difficulties in picking operations that kit materials to assembly lines be resolved? 3. How can a model be developed that facilitates improvements concerning work balancing picking operations in relation to varying demand? Method – Through a summary, major difficulties are identified with support of literature studies, interviews, observations and documentation performed at a case company. The collected data form the base of the developed work-balancing model aiming at allowing users to work balance their picking operations. Findings – Initially, a comparison between literature studies, interviews and observations at the case company revealed five major difficulties: lack of parts, order handling, warehouse maintenance, standardization of picking operations and work balancing. When the first three difficulties are improved, a standardization of processes should be performed in order to achieve process perfection. Furthermore, as a last step in the developed four-step-improvement-process, work balancing could lead to improved resource utilization. Moreover, work balancing the picking operation at the case company through the developed model resulted in a reduced balancing loss of 39%. Research limitations – The conducted case study is structured as a holistic single case study. Since companies differ it would be appropriate to conduct multiple case studies in order to generalize results. Furthermore, the authors want to expand the extensive literature studies to identify all difficulties and alternative solutions. Nevertheless, this is not achieved in relation to the scale of the work and time limitations. Further research – If performing a similar investigation other factors need to be taken into consideration regarding gathering of time studies such as lack of parts, picking errors, deficiencies and other interruptions, this in order to acquire a accurate company reflection due to more precise measurements. Key words – Lean production, work balancing, kitting, improvements, standardization, picking operation, varying demand