Structural interviews were conducted with 66 children and their families to investigate how the experience of pain varied during cancer treatment. At diagnosis, 49% experienced cancer-related pain. Intense pain was more common at the beginning of treatment when it was often believed that pain treatment could be better. Procedure- and treatment-related pain were the major problems initially. Procedural pain gradually decreased, but treatment-related pain was constant and dominating. For some procedures pain was rated highest initially, lower during the second period, and higher again during the final part of treatment. Pain intensity measurement was seldom performed, and parents increasingly considered themselves better judges of their child's pain than professionals. Increased knowledge about pain and pain treatment in children with cancer, where most pain is iatrogenic, will help us to meet the needs and demands of children and parents, and to reduce pain to a minimum.