This paper reports an analysis of the relative influence of work-related, care-related and personal factors on carer outcomes among 204 working female carers. To examine the importance of personal factors, the ‘Motivations in Elder Care Scale’ (MECS) and the ‘Relationships in Elder Care Scale’ (RECS) were developed. In a qualitative pilot study, interviews with working-age carers were drawn on to form the items for inclusion. The MECS included items for external pressures to care, e.g. guilt, the older person's expectation of care, and perceived disapproval of others, and for internal desires to adopt the caring role, e.g. carer's resistance to other forms of care, living up to one's principles and caring nature. Psychometric tests revealed that two subscales had greater reliability, the EXMECS (extrinsic motivations to care) and the INMECS (intrinsic motivations). The RECS included both positive items, e.g. respect, admiration for the older person, and lack of generational differences, and negative relationship items, e.g. struggle for power, and older person's resistance to caring efforts, and had good reliability. Measures of carer stress and carer satisfaction were included as outcome variables. Multiple regression analyses showed that the RECS and the MECS were the most significant predictors of carer outcomes. Greater extrinsic motivations to care and poorer quality of the relationship with the older person were the most significant predictors of carer stress. Better relationship quality and greater intrinsic motivations to care were the most significant predictors of carer satisfaction.