Background: Over the past 15 years Punta Arenas, Chile, a medium-sized city located on the extreme southern tip of South America, has repeatedly been exposed to acute, sudden episodes of highly increased levels of ultraviolet B (UVB) 280-320 nm radiation because of the passage of the spring Antarctic “Ozone Hole” overhead, or nearby. Objective: Our purpose was to observe the relationship between episodes of ozone depletion, increased UVB radiation, and sunburns and photosensitivity disorders in Punta Arenas, Chile, during spring. Methods: Incidence of photosensitivity disorders and sunburns was registered by dermatologists during each of the past 15 springs. Local data of sudden, severe ozone depletions (<250 Dobson units) and the corresponding increase of UVB radiation were reviewed. Results: Patients with sunburn increased significantly during the austral spring of 1999 (P < .01). This was especially noticeable (29/31 cases) on weekends with ozone depletion, and increased UVB radiation (P < .01) occurred on the Sundays Oct 31, Nov 21, and Dec 5, 1999. The incidence of photosensitivity disorders, although statistically not significant, increased 51% over the past 7 years. Conclusions: An acute impact on human health (sunburn) occurred because of abrupt ozone depletion and the accompanying increase in UVB during the mid and late austral spring of 1999. Most sunburns (93.5%) occurred on weekends. Ozone levels as well as seasonal and recreational factors played a mayor role in the increase in sunburns. The increase in radiation at 300 nm, the most carcinogenic wavelength, on days under the Antarctic ozone hole is a matter of special concern. (J Am Acad Dermatol 2002;46:193-9.)