In this paper we introduce a multi-modal database for the analysis of human interaction, in particular mimicry, and elaborate on the theoretical hypotheses of the relationship between the occurrence of mimicry and human affect. The recorded experiments are designed to explore the relationship between the occurrence of mimicry and human affect. The corpus is recorded with 18 synchronised audio and video sensors, and is annotated for many different phenomena, including dialogue acts, turn-taking, affect, and head, hand gestures, body movement and facial expression. Recordings were made of two experiments: a discussion on a political topic, and a role-playing game. 40 participants were recruited, all of whom selfreported their felt experiences. The corpus will be made available to the scientific community.