To describe the clinical population of women admitted to a Mother-Baby Unit in Adelaide, South Australia and to evaluate changes during admission in both Axes I and II diagnoses of maternal mental health, and in mother-infant relationships. Both clinical and self-report assessments of maternal mental health were made at admission and discharge, and self-report comparisons of the mother-infant relationship. Depressive illnesses (46.2%) were found to be the most prevalent conditions leading to admission, with rates of psychosis (10.3%) and bipolar disorder (3.4%) being lower. A high incidence of borderline personality disorder (23.1%) was found clinically, with almost half the admitted women showing features of borderline personality disorder on a self-report measure at admission. Significant improvements in maternal mental health and the mother-infant relationship were found at the time of discharge. Admission to this Mother-Baby Unit on mothers' self-report scales showed improvement in mothers' mental health and the relationship that they have with their infant. Given the high prevalence of borderline personality disorder and emotional dysregulation identified within the population, treatment implications and possible consequences for the infant are discussed for this client group.