Little is known about the factors that mediate the caregiving experience of informal carers at home, which could inform about ways of supporting them in their caregiving role. Our objective was to investigate the caring experience of carers for patients with an advanced progressive illness (chronic obstructive pulmonary disease [COPD], heart failure, cancer, or motor neuron diseases [MND]), who suffer from breathlessness. A purposive sample of 15 carers was selected. They were recruited via the patients they cared for (who suffered from COPD, cancer, MND, or heart failure) from the hospital and the community. Data were collected through semistructured, in-depth interviews. All were tape-recorded and transcribed verbatim. The analysis used a Grounded Theory approach and NVivo software facilitated the management and analysis of the data. Several key issues affected caring in a positive or a negative way. The threats to caring were uncertainty, carers' own health problems, an imploded world, negative reactions from outside, person loss, and acute exacerbations. Resources that carers drew on were acceptance, self-care, availability of support, feeling that caring is a shared responsibility with the patient, and "getting on with" caring in case of emergencies. Breathlessness was particularly challenging, and carers did not have any strategies to relieve the symptom. They were ill prepared for acute exacerbations. Carers need to be included in opportunities for support provision in advanced illness. Negotiated involvement of a health professional could buffer the heavy responsibilities related to home care. They could provide problem-solving skills and build on the resources that carers draw on in response to what they experience as most threatening to their caring role.