Monoclonal antibodies have become an important new class of therapeutic agents approved for use in solid tumors. They function through several different mechanisms including inhibition of tumor-related signal transduction, induction of apoptosis, inhibition of angiogenesis, enhancing host immune response against cancer and targeted delivery of cytotoxic agents to the tumor site. Several monoclonal antibodies have now received regulatory approval--trastuzumab, cetuximab, panitumumab, bevacizumab, catumaxomab, ipilimumab and denosumab--across multiple solid tumor types, including breast, colorectal, head and neck, non-small cell lung cancers and melanomas, amongst others. These agents are employed clinically in some neoadjuvant/adjuvant and radical treatment settings, as well as more extensively in the metastatic and palliative settings. Current research is focused on innovative compound design, novel targets, predictive biomarker discovery, enriched patient populations, and combination strategies in order to overcome resistance and prolong disease control. Here we provide an overview of monoclonal antibodies approved for use in clinical oncology and those currently in clinical development.