Several insulin analogues have been developed in recent years and are increasingly being used in the treatment of diabetes. However, modifying the insulin molecule not only changes its metabolic effects, but can also alter its mitogenic potency. In vitro experiments had previously suggested a potential association between insulin analogues and cancer. In 2009 several articles were published in Diabetologia describing an association between administration of glargine (Lantus) and higher incidence of cancer rates. The present article aims at briefly presenting the state of the art based upon currently available data on insulin and cancer. We will summarize the mechanisms by which insulin can increase cell proliferation, the observations reported in recent publications and finally conclude with some practical recommendations.