This research study is designed to assess the trafficking pattern of autologous monocytes when given intravensously to humans. Monocytes will be removed from normal volunteers or from cancer patients by cytapheresis and purified by counter-current centrifugal elutriation. The purified monocytes will either be left at 4 degrees (normal monocytes) for 4 hours or be activated by exposure to recombinant human gamma interferon. The cells will be labeled with Indium-111 and infused intravenously back into the normal donor or patient, respectively. Normal donors or cancer patients will first be given an intravenous infusion of autologous normal monocytes; if no untoward reactions are noted, the donors or patients may receive infusions of autologous gamma interferon- activated monocytes four weeks later. Frequent blood samples will be withdrawn from the patient or donor over the ensuing 96 hours to determine the rate at which the infused cells equilibrate with the marginating pool of blood monocytes (if one exists), and to determine the rate at which these cells emigrate from the bloodstream to enter the reticuloendothelial system and other tissues. In addition, multiple regional scintigraphs will be obtained to determine if these labeled monocytes preferentially localize to any one organ system. This information will further our understanding of the normal physiology of activated and unactivated monocytes and, in addition, hopefully will allow us to more rationally design adoptive immunotherapy trials in which purified autologous cytotoxic blood monocytes will be given to cancer patients intravenously.