For many patients, injectable filling agents offer the promise of facial rejuvenation while offering reduced risks compared with more invasive surgery. With the increase in products available and the rise in the number of patients seeking this type of intervention, it is crucial that both the physician and the patient are fully cognizant of the risks involved with each product. To review the incidences and types of reaction to various commonly used injectable products. A literature review and personal experiences (gained largely in Europe over the past 8 years) of dermal fillers from 1996 to the present, including illustrative case reviews. Reactions can be attributed to the procedure itself, the procedural technique, and the agent injected. Some of these reactions are preventable, whereas others are inevitable; most are mild and transient. Improving product formulations, altering the concentration of product injected, or changing the injection technique can dramatically reduce the incidence of adverse reactions. Since its reformulation in mid-1999, the biologically engineered hyaluronic acid filler Restylane (Medicis Pharmaceuticals, Scottsdale, AZ, USA) elicits less than one allergic reaction in 1600 treatments. Skin reactions with poly-L-lactic acid (New-Fill/Sculptra, Dermik Laboratories, Berwyn, PA, USA) are considerably less likely if a greater dilution and deeper injection technique are employed. Different injectable products have highly divergent properties, associated risks, and injection requirements. The dermasurgeon should be suitably experienced to select and use these products correctly.