NovoPen, the first insulin pen injector, was introduced in 1985. This article reviews the published evidence over two decades of use of the NovoPen family of injection devices in diabetes management. A search for NovoPen publications from 1985 onwards was conducted in the following databases: MEDLINE/PubMed, Cochrane Database of Systematic Reviews, American College of Physicians Journal Club, Database of Abstract Reviews and Effects, and Cochrane Controlled Trials Register. Publications were examined and underwent a selection process to identify studies of NovoPen devices (NovoPen , NovoPen 2, NovoPen 1.5 and NovoPen 3) in the diabetes/insulin therapy area that contained evidence of the effects of NovoPen in a variety of categories. Of the studies identified, most showed that insulin regimens using the NovoPen family of devices are at least as effective (and in some cases superior) in maintaining glycaemic control and are as safe (in terms of hypoglycaemia) as conventional insulin regimens employing syringes. The published evidence identified also showed that insulin administration via NovoPen devices was for most patients easier, more convenient and quicker than with conventional syringes and that most patients preferred the various NovoPen devices over syringes. There was also some evidence that the use of discreet devices, like those of the NovoPen family, facilitates adherence to intensive insulin therapy regimens, helps to improve lifestyle flexibility and reduces injection pain compared with conventional syringe-based regimens. Together these benefits of NovoPen devices are considered likely to improve both patients' quality of life and compliance with therapy. In conclusion, a large body of published evidence accumulated over the past two decades testifies to the patient-related benefits of the NovoPen family of insulin injection devices in the treatment of diabetes.