Treatment with injectable tissue fillers for aesthetic purposes is increasingly popular. In parallel with this success, questions related to the safety of these treatments and the products involved are being raised more prominently. To gain insight in the safety aspects of injectable tissue fillers, we performed a literature review to collect studies reporting clinical data of injectable tissue fillers. We found several case reports where serious complications after more than three years are described. However, there are only a limited number of well-defined prospective clinical studies available with follow-up periods longer than three years. Furthermore, causes of complications, that is, treatment or product related, are often not specified in literature. Considering the intended functional period of fillers in combination with the known occurrence of long-term complications, there is a need for well-defined prospective clinical studies. In order to be able to discriminate between product failure (a product safety issue) or application methodology (a physician expertise or training issue), better identification of observed complications and whether they are product or treatment related, is needed. For the safe use of the fillers it is important that treatment with injectable tissue fillers is performed by a trained physician, who knows the product specifications and its applications. . Moreover, it is expected that due to increase in life expectancy, the demand for anti-aging treatments, like tissue augmentation with injectable tissue fillers, will grow [2]. Their success has been attributed to the fact that treatments with injectable tissue fillers are fast and appear to be relatively easy [2]. Only a relatively 'simple' subcutaneous injection is needed. Today, various injectable tissue fillers with different characteristics are available, for example, duration of the effect, material type and intended anatomical location.Although the application of an injectable tissue filler seems to be relatively simple and safe, reports of serious adverse effects have appeared in the literature [2][3][4][5][6][7][8]. Estimates of the occurrence of severe complications after treatment with various types of injectable tissue fillers range between 1:80 and 1:50,000 patients [9,10]. Adverse side effects can be caused by incorrect injection techniques (treatment related) or by the characteristics of the products (product related) [11,12]. Short-, mid-and long-term complications can be discerned (TABLE 1) [2,13-15]. Short-term complications like pain, swelling, fever, immediate hypersensitivity reactions, occur immediately or within several days past treatment and disappear after several weeks. A more severe short-term complication is necrosis [5,16]. Necrosis occurs immediately or within a few days if blood vessels are obstructed by the filler material or if they are injured during the treatment [17]. Mid-term complications such as delayed inflammatory reactions, ulceration and granuloma reaction may occur after 2-12 months. I...