The objectives of this study are to describe caregivers' subjective burden and to identify the predictors of burden in primary caregivers of mentally ill outpatients recruited from eight hospitals in Montreal, Quebec, Canada. Patient and primary caregiver variables, were regressed on perceived burden using hierarchical regression analysis. The variables describing the patient's current state contributed the most to explaining variance in subjective burden. The variables related to psychiatric history and to outpatient treatment also explained a significant proportion of the variance in the burden scores. Better understanding of the factors associated with subjective burden will enable researchers and practitioners to identify those caregivers that are at greater risk for higher levels of burden, and to develop more focused and appropriate interventions.