While infant behaviour is influenced by maternal care, infant crying and dysregulated sleep can reciprocally affect maternal mood. The temperament and behaviour of two 4-12-months-old infant cohorts admitted with their mothers to a residential parenting program were examined using behaviour charts and the Short Infant Temperament Questionnaire (SITQ). One group was re-assessed one and six months later. Infant temperament was significantly more difficult than population norms and most had dysregulated sleep. One month after treatment, total infant crying and fussing, frequency of night-time waking, and sleep and feeding dysregulation were significantly (p less than 0.001) reduced, with change sustained at six months. Easy-Difficult scores (SITQ) were stable and significantly worse than population norms. The contribution of a "difficult" infant temperament to maternal mood disorder warrants further investigation. (Contains 5 tables.)