**1. Introduction**

Modern advances and a quantum leap in the field of cancer therapy has been promising to oncologists with new tools to fight many cancers. The immune system has multifunctional units referred to as antibodies, mostly polyclonal which facilitate humoral and cellular reactions to antigens [1]. However, it is possible to produce large quantities of an antibody from a single B-cell clone which are called as *Monoclonal Antibodies (MAbs).* Using these antibodies for therapeutic purposes is termed as Immunotherapy. Immunotherapy in recent times has been propitious across a number of cancer types. Stimulating results with MAbs directed towards both established and emerging targets indicate its potential key role as a therapeutic agent [2]. These are being tested in earlyand late-stage clinical trials. In the last 35 years over 100 Monoclonal Antibodies have been considered potential as drugs and many have been approved. The usage of the monoclonal antibodies in cancer therapy requires the understanding of the biological role of various antigens involved in tumor growth [3]. In cancer patients' immunity system is often altered. The purpose of immunotherapy with monoclonal antibodies is to interfere with synergic activity of immunosuppressive environment created by T cells, cytokines, interleukins and tumor growth factor [4]. In many cancer treatments, the monoclonal antibodies have been robust enough, however in some, combinatorial treatments including monoclonal antibodies, chemotherapy and vaccines have been successful thereby bringing together cancer immunologists and clinicians required for the management of cancer in the near future [5]. This chapter will focus on Immunotherapy using Monoclonal antibodies for many urologic oncology types such as prostate, renal, bladder, testicular and penile with a hope to highlight its clinical utility and also its mechanisms of action in each of these cancer types.
