Background: Mood disorders are common in Chile. Among these, post partum depression (PPD) deranges the maternal and family relationships. Aim: To determine the prevalence and risk factors associated with PPD in puerperal women in Temuco, Chile. Material and methods: The Edinburgh Postnatal Depression Scale was administered to 73 puerperal women aged 15 to 32 years, between 40 to 45 days after delivery. To detect risk factors, 20 women with and 20 women without post partum depression (PPD) were interviewed and their clinical records were reviewed to assess their perinatal care. Results: The prevalence of PPD in the whole sample was 50.7%. The individual psychological risk factors detected were a feeling of discomfort with their body after giving birth, a personal history of mental health problems and a high level of overload associated to child care. An individual physical risk factor was alcohol consumption during pregnancy. Family risk factors were a poor relationship with the father of the child during pregnancy, a history of mental health problems in close family members, a history of family violence and a poor realtionship with parents during puerpurium. Having more children was a sociodemographic risk factor. Conclusions: Pospartum depression is common. The characterization of risk factors should lead to the implementation of preventive strategies (Rev Méd Chile 2008; 136: 44-52).