The U-Men is an organization of fanatical humans who believed in the doctrines of transpeciesism to become physically superior by essentially becoming Mutants. The group believed that using stealing and grafting mutant body parts through surgery, employing unethical genetic modification procedures, and injecting mutant blood transfusions and X-hormone mutagens into their members would create the Third Species, humans empowered with mutant abilities. To that end, they have abducted and have been responsible for the deaths of many mutants for the sake of experiments and organ harvesting through illicit organ smuggling operations to make their members more like mutants. They have encountered students at the Xavier Institute on several occasions.

During one of those events, U-Men were detected by Xorn's special class and a battle ensued, whereupon Angel Salvadore destroyed a car with U-men presumably inside. On another occasion, the Omega Gang, lead by Kid Omega crashed into a U-men base, during a surgical transfer of body parts, killing the half dozen members.

They wear suits that are suppose to keep them pure, these suits were identified as expensive.