Allowing a suffering patient with cancer to control his pain is a challenge that numerous medical teams intend to take up. Although the best treatment is the etiologic one, in many situations the symptomatic and adjuvant therapies are both indispensable. Among them, the patient controlled analgesia (PCA) is a concept referring to the management of the pain, but also to the administration of some analgesic drugs. Even with genuine advantages the limits of the PCA do exist and need to be well known. PCA is not limited to palliative treatment; it can be used in many circonstances during each evolutionary step of the cancer, temporarily or for longer periods, at the hospital and at home as well. All patients disposing of such an equiment could determine their own best level of analgesia, at the good time, depending upon the temporal variability of the pain and its previsibility or not. The availability and the pedagogic concern of the members of the team, the link between the patient and his family, the involvement of both the regular general practioner and the "algologic" team are essential to maintain the best effects of this method.