Background: To establish the knowledge, about sun exposure and photoprotection in outpatients treated at the dermatology clinics in four hospitals in Lima, Peru. Material and Methods: A cross-sectional study was conducted involving a sample of 364 patients selected using a systematic random sampling process in the four participating hospitals. The selected patients were interviewed to determine their knowledge, behavior and practices in relation to sun exposure and photoprotection. The chi-square test was used to identify any significant differences between knowledge and practices. Results: The mean age of the patients in this sample was 45.1 ± 21.4 years. Of the 364 patients, 55.9% were women and 54.8% had skin phototype IV. The principal risks related to sun exposure were skin cancer (80.5%) and sunburn (77.8%). Knowledge regarding sun protection was more evident in individuals with university/college education (p<0.001). In addition, 78.9% of the individuals reported that they knew about photo-protectors and 52.3% stated that they used them regularly. In general, women were more knowledgeable regarding sun protection (p=0.001). Of the total number of users of photoprotection, 38.4% used these products daily, while 61.6% used them only occasionally. The use of photo-protectors differed significantly in accordance with the individual's education level (p<0.001). In the majority of cases there was a statistically significant difference between knowledge and practice with respect to solar protection. Conclusions: The level of awareness of the outpatients treated at the dermatology clinics in these four hospitals in Lima, Peru about the risks of sun exposure is acceptable; however, a large proportion fail to incorporate regular solar protection as a practice in their daily life. © 2011 by Anais Brasileiros de Dermatologia.