Abstract: Field studies and user requirements analysis are highly valued practices in the human-computer interaction community. However, in companies, field study methods are not widely used and they still encounter resistance. In this paper, we describe a longitudinal research effort conducted in two companies to introduce field studies and make them a part of the product development process. A strategy called “Trojan horse” was developed in order to make the adoption of field studies easy and motivating in real development contexts. The strategy consists of four complementary parts: (1) introducing field studies using small-scale pilots, (2) applying a start-up package, (3) making field studies simple and flexible, (4) presenting the field study findings in a form that is familiar and easy to implement in product development. After two years' follow up, the results show that the strategy has been effective and the impact is longstanding in the two case companies.