BACKGROUND About 1.4 million new cancer cases are expected to be diagnosed in the US in 2008 and the overall costs of cancer treatment is estimated at > $200 billion per year. Over half a million people will die from cancer each year. Monoclonal antibodies have attracted attention because of their potential clinical benefits. Currently, there are four monoclonal antibodies that have been approved by the FDA for the treatment of solid tumor malignancies. Over 100 other antibodies are in early- and late-phase clinical testing. OBJECTIVE Clinical efficacy of FDA-approved and investigational monoclonal antibody therapies are summarized. CONCLUSIONS Anti-tumor responses have been modest. However, the advent of novel antibody engineering and combination therapy strategies has generated much optimism for current and future antibody-based therapeutics in solid tumors.