To evaluate dose rates and daily doses (DDE) at Valdivia in Southern Chile, ultraviolet irradiances recorded every 15 min from 1998 to 2000 with a high resolution spectroradiometer were weighted with an erythemal action spectrum. Exposure times to get one MED (210 J/m2) in Summer are 10, 12, 18 and 24 min for skin types I trough IV respectively. DDE estimations included in NASA Web products overestimate measurements by 16% on average in Summer, with an absolute uncertainty of 980 J/m2 at the 95% level. Observed dose rates for clear days are in fair agreement with the numerical output from a numerical model, suggesting that acute episodes can be predicted if total ozone can be forecasted and the population is instructed on corrections for cloud effects (Rev Méd Chile 2002; 130: 17-25)