This paper presents the multimodal corpora that are being collected and annotated in the Nordic NOMCO project. The corpora will be used to study communicative phenomena such as feedback, turn management and sequencing. They already include video material for Swedish, Danish, Finnish and Estonian, and several social activities are represented. The data are being annotated following an annotation scheme that provides attributes concerning the shape and the communicative functions of head movements, face expressions, body posture and hand gestures. The paper also discusses how the corpora will be used to study the way feedback is expressed in speech and gestures, and reports results from two pilot studies that have been conducted on this issue. The annotated corpora will be valuable sources for research on intercultural communication as well as for interaction in the individual languages.