Important arenas for interaction on critical interfaces (sales – design – production) in industrial firms are the various meetings where groups come together around a common task. The purpose of this dissertation is to contribute knowledge about the interactions that occur within and between work groups in their handling of their tasks in small industrial companies (SME’s) and the significance of these interactions on learning and effectiveness. The thesis focuses especially on the following questions: 1. What characterizes the interaction within and between work groups as they are expressed in various meetings? 2. What factors facilitate and hinder the interaction within and between work groups? 3. What are the consequences of different kinds of interaction regarding learning and effectiveness in work groups and in organizations? The study takes a critical realistic perspective on learning in organizations and is based on previous studies on learning, communication and effectiveness in groups and organisations. The study was conducted during 2008-2010 and used a qualitative and interactive approach. The collection of data was based on interviews, observations of video filmed meetings and on questionnaires. The analysis moves between two levels: interaction within groups and between groups at an organizational level. The interactions within and between groups were analysed based on contextual factors in order to understand whether different communication patterns were related to different types of learning and effectiveness. A rationalistic concept of effectiveness was challenged in favour of a humanistic approach where learning is an important aspect. Three major conclusions were drawn: Effectiveness presupposes that patterns of communication and management are tailored to the task at hand – performance or development. Feedback and links between groups need revision and steering to facilitate interaction. Discrepancies (contradictions, conflicts and disturbances) that are made visible in the organization may lead to development. Those remaining in the hidden disturb the performance.