Exposure to ultraviolet (UV) radiation is a major environmental risk factor in the development of skin cancers and it occurs mainly during outdoor activities. The purpose of this study is to quantify the UV exposure suffered by amateur athletes (tennis players, hikers and runners) in their training schedules. The study on tennis player exposure took place at a tennis club in Valencia during the month of June 2011. With respect to the hiking group, the hikes studied took place in several mountainous areas of Spain and France from June to August 2011. Finally, the exposure suffered by ten runners while participating in a running circuit in the province of Valencia, from March to November 2011, was studied. The athletes were monitored using personal dosimeters (VioSpor), with the tennis players and runners wearing them on the wrist and the hikers on the shoulder. The median daily personal UV exposure for the hikers was 8.1 Standard Erythema Dose (SED) and for the tennis players 7.5 SED per day of training. The runners received a median of 14.6 SED while participating in the running circuit and about 2 SED per competition day. Median daily UV exposure of the hikers and tennis players exceeded 5 SED, which means that, in the case of non-sun-adapted skin type III and the non-use of sun protection, erythema may be induced in these subjects. However, the exposure suffered by the runners did not exceed the maximum personal exposure of 5 SED. Accordingly, it is necessary to encourage the use of high protection sunscreens and protective clothing and to avoid UV exposure in the hottest part of the day.