The correct insulin application is an important aspect of a successful insulin therapy. Today, we have devices, which make insulin therapies easier to handle, socially more acceptable, and safer Of these, insulin pens are the most frequently used devices. This paper summarizes the particular knowledge necessary for correct and precise instruction of patients with regard to the choice of the pen and the fitting syringe as well as details of the correct use of the different pens. The injection technique itself does not differ from the one with syringes and needles. Nevertheless, some important aspects are pointed out.