This research studies social representations of cancer and chemotherapy with patients (N = 62) and of oncologists (N = 26) in a medical oncology unit. The collection of the data was made from free association tasks (concerning cancer and chemotherapy) and attitude questions concerning chemotherapy. Patients also had to produce representations "for" oncologists and conversely. Results indicate a variety of representations marked by the status of sample (patients versus oncologists). The stressful component of the disease is very present. Contrary to the patients, oncologists seize relatively well the representation, which the patients have of concerning cancer and chemotherapy. Patients' representations are connected with phenomena of belief that give evidence for some process of anticipation and expectation linked to the experience of illness and testify the emotional charge related to it. The study of the representations is particularly relevant to highlight the psychosocial stakes associated with the therapeutic situation.