Fifty-four young professionals in their first job after apprenticeship described their task-related and private interactions at work during five days, using a variant of the Rochester Interaction Records self-observation method (Reis and Wheeler, 1991). Results showed that more task-related interactions were reported than private interactions at work. The latter are described as more personally meaningful and more often initiated by the person or mutually initiated than task-related interactions. The number and duration of task-related interactions depended on the profession and the working conditions. The individual's own activity level during task-related interactions was predicted by social skills, measured 6 months before the diary study. Frequency of private interactions at work depended on familiarity level with colleagues. After controlling for role ambiguity and social stressors, more interactions and higher satisfaction with interactions at work predicted affective commitment, and more interactions at work also predicted job satisfaction. The study highlights the importance of conducting micro-analyses of social interactions at work.