We present in this paper a new multimodal corpus of spontaneous collaborative and affective interactions in French: RECOLA, which is being made available to the research community. Participants were recorded in dyads during a video conference while completing a task requiring collaboration. Different multimodal data, i.e., audio, video, ECG and EDA, were recorded continuously and synchronously. In total, 46 participants took part in the test, for which the first 5 minutes of interaction were kept to ease annotation. In addition to these recordings, 6 annotators measured emotion continuously on two dimensions: arousal and valence, as well as social behavior labels on live dimensions. The corpus allowed us to take self-report measures of users during task completion. Methodologies and issues related to affective corpus construction are briefly reviewed in this paper. We further detail how the corpus was constructed, i.e., participants, procedure and task, the multimodal recording setup, the annotation of data and some analysis of the quality of these annotations.