Patients diagnosed with cancer are frequently prescribed radiation therapy. The treatment is a source of much anxiety and worry for patients and their families. Support, a highly valued intervention strategy in nursing, is believed to assist patients to adjust to stressful experiences. A qualitative study was conducted to determine patients' experiences of support while receiving radiotherapy. Data from 12 patients were analysed using the procedures and techniques of grounded theory. A substantive theory of support emerged which showed that support is an interpersonal process embedded in an array of social exchanges which involves encountering support, recognising support and feeling supported. Three main types of support are encountered: being there, giving help and giving information. It is a multifaceted concept and all types of support are seen as important. Actions are interpreted within the norms and expectations of a relationship and labelled as supportive by the recipient. Family and friends are the principal sources of all types of support. Professional support is mainly informational. The findings raise many questions, one of which is should there be a rethinking of the concept of support in nursing?