Repeated exposure to UV radiation from the sun causes premature skin aging. This photoaging is characterized by wrinkles, mottled pigmentations, dry and rough skin, and loss of skin tone. Since the clinical demonstration that the use of topical tretinoin can improve photoaged skin, a great deal of knowledge that may explain wrinkle effacement has been acquired. Central to this pursuit has been dermal collagen. In this article, we summarize evidence (mainly from humans) that implicates a deficiency of superficial dermal collagen as the cause of the dermal aspects of photoaging. In addition, a mechanism through which UV radiation can lead to reduced collagen is presented. Through our understanding of the pathophysiological mechanism of photoaging, our ability to treat and possibly prevent this skin condition is enhanced.