Specific patterns of interaction emerging in the first months of life are related to processes regulating mutual affects in the mother-child dyad. Particularly important in this respect are the processes of ‘matching’ and ‘interactive repair’. According to previous research results, these interaction processes are significantly impaired in mothers with postpartum depression, exerting a detrimental influence on the infant's emotional and cognitive development as well as on the course of the mother's illness. It is not yet clear, however, whether a recovery from depression is also connected to a favourable development of these interactional behaviour patterns. The study will correlate patterns of interactive affect regulation in the first months of life with the course of the mother's depressive illness. To achieve this, interactions of mothers with postpartum depression and their infants will be evaluated using the Still Face Design at two assessment times (T1: acute phase of depression, T2: remission). Results will be compared to a control group of healthy mothers with age- and sex-matched children. Clinical and theoretical implications will be discussed.