We examined determinants of carer strain in a random sample of 170 relative of dependent elderly persons in Sweden aged 80 years or more. These persons were interviewed at home by means of the Sickness Impact Profile (SIP). Carer strain was assessed in interviews with carers who bore the main responsibility for care of an elderly relative. The response rate was 92%. Multiple logistic regression showed that cohabitation of carer and recipient was the sociodemographic variable most significantly associated with various stress factors and consequences or manifestations of stress; strain connected with ADL assistance given to the elderly person, strain arising from the elderly person's uncooperative or recalcitrant attitude or behaviour, worsening of the elderly-carer relationship, and encroachment on the carer's social life. Correlations between strain and various categories of physical and mental impairment were much lower, and in some respects were even negative. We conclude that support programs for relatives caring for dependent elderly persons should aim primarily at creating continuous relief for the carers and improving their opportunities for contact with other people generally.