Patients currently taking IL-2 by subcutaneous injection (under the skin) may participate in an optional part of the study to receive future IL-2 cycles at home instead of at or near the Clinical Center. Patients who have shown an ability to self-administer and tolerate IL-2 injections with minimal supervision and minimal side effects may be eligible for this option. Home administration of IL-2 involves less frequent data and safety monitoring, and no on-site medical evaluation at the very beginning of each cycle. Participants will continue to be seen at the Clinical Center for regularly scheduled follow-up visits and medical evaluations before the start of each IL-2 cycle to determine if it is safe to begin that cycle. Patients will have a case manager who will place monitoring calls on days 2 and 4 of the cycle and a third follow-up call 1 week later. Patients will be responsible for contacting a study staff member if complications of other problems develop at other times.