The pyrroloquinoline quinine is a cofactor discovered in bacteria. It is associated with various bacterial soluble and membrane enzymes that directly oxidize sugars, alcohols, aldehydes. In higher organisms, it has been reported that pyrroloquinoline quinine acts as a potent free radical scavenger and it seems to intervene in different processes causing remarkable benefits. One of the most important effects is that pyrroloquinoline quinine induced apoptosis in different cancer cell lines. It is interesting to observe the role of pyrroloquinoline quinine as pro-apoptotic agent. This review shows the most relevant aspects of this cofactor and its antiproliferative effects.