This chapter presents a detailed protocol for the generation of mature, monocyte-derived dendritic cells (DC) that are loaded or "pulsed" with tumor-associated peptide antigens for use as patient-specific immunotherapy. The protocol can easily be adapted for the treatment of patients with a variety of tumors or chronic viral infections by simply changing the peptide antigens used. The vaccine may use major histocompatibility complex (MHC) class I- or class II-restricted peptides to elicit stimulation of CD8+ cytotoxic T-lymphocytes (CTL) or CD4+ T-helper cells, respectively. It also provides an example of loading DC with a purified protein antigen-in this instance, keyhole limpet hemocyanin (KLH). KLH may be used to boost the immunogenicity of the vaccine and as a control to test for the induction of CD4+ T-helper-cell responses. Other antigenic proteins may be added or substituted. Once prepared, the DC are frozen in aliquots and samples are tested for identity, purity, viability, and sterility. After these "release" criteria are met, vaccine aliquots can be thawed, drawn up into syringes, and injected back into the patient.