Work communications involve both interpersonal relationships and information to be conveyed. Ergonomics has generally neglected the first dimension, whilst emphasising the latter. We question this position using a field study that is conducted in an industrial environment, and which highlights the role of interpersonal trust in communication effectiveness and reliability at shift handover. Before presenting the methodological approach and the results of this study, a conceptual framework for understanding the dynamics of interpersonal trust is described. It combines antecedents of trust, trust levels and their immediate effects conceived as negotiated and implicit expectations on the one hand, and a monitoring strategy on the other. This monitoring strategy aims to insure as much as possible that trustors? expectations will be satisfied or, if not, that they will understand why this has not been possible. Later, some events are observed by trustors (e.g., trustees? behavior or outcomes). Trustors compare them to their expectations, leading to a consistency judgment. If inconsistencies are detected, explanations are sought. Based on the explanations revealed, trustors may decide either to reinforce their initial beliefs or, on the contrary, to downgrade them, which will affect their subsequent collaboration with the trusted party. This model was useful not only to make sense of the data collected through our initial observations and interviews in the industrial setting, but also to assist a work group that includes the different stakeholders in their search for solutions to improve the reliability of their shift handover. Overall, the study shows that trust or distrust relationships directly influence the workers? decisions to convey information or not, the choice of the information to be conveyed and its interpretation. These factors have actually proven to be essential in elaborating a socio-technical device for shift handover and making it more easily acceptable.