Field studies, interviews and participative observations have been the main methods in this master thesis where the author has studied, and partially participated, in the development process of a booking system called FRI. Idavall is the small company that develops this suc-cessful software despite small resources. Characteristic for Idavall is in the way they manage to involve their about 1300 users in the development process. The development process is highly flexible which is required when rapidly changes are common. The overall question in this thesis is: How do Idavall manage to develop this software in a flexible way and successfully involve their users in the development process? Idavall arranges FRI-meetings, courses and demonstrations where users meet each other and a representative from Idavall. All participants discuss FRI and have the opportunity to propose changes, improvements and report bugs. One of the most important parts of the busi-ness idea of Idavall is to offer a proper, friendly and professional support. The support is one of the most important possibilities to be informed about the users? needs, wishes and propos-als. This, what I called, user driven development has a lot of common with Participatory De-sign (PD) where users participate in the design of new software. PD implies that users of software should take part in decisions that affect the system and the way it is used and de-signed. Idavall make use of a kind of Customer Relationship Management (CRM), which is a concept used in the marketing arena. The objective of CRM is to create a strong, mutual and trustful relationship between supplier and customer. By using CRM in combination with PD it is possible to enhance the user participation and enable user driven development. The company has a flexible development process, which is built on an informal way of driving the process. Informal meetings are common where decisions about changes and im-provements are taken quickly. New versions are delivered about 20 times a year. The employ-ees meet several times a day in the central located coffee room and discuss problems. The development process has a lot of common with Extreme Programming (XP), which is a software development methodology that aims to make software development more flexi-ble and focus on highly flexible environments with quickly changing requirements. XP is de-scribed briefly and comparisons are made to the development process of FRI as well as short-comings of XP in the context of PD.