This paper presents an experimental study made on the use of different kinds of information sources in manual assembly. The general idea is that only the necessary information should be presented to the worker and it should be presented where and when the worker needs it as this is believed to both save time and unload cognitive strain. To account for the latter two aspects of this thought, where and when, this paper investigates the use of a handheld unit as an information source in manual assembly. Having a mobile information system, such as a Personal Digital Assistant (PDA), that can be carried with you at all times, as opposed to a stationary one, such as a computer terminal, is hypothesized to greatly improve productivity and quality. Experimental results show that the use of a PDA significantly improves quality whereas productivity does not significantly improve.