The Quelccaya Ice Cap in the easternmost glaciated mountain chain of the Peruvian Andes has been studied in four recent field seasons. Ice cores to a depth of 15 meters have been retrieved at the summit dome (elevation, 5650 meters) and two other locations and used for microparticle, isotope, and beta radioactivity measurements. A concurrent study of the present climate and the heat and mass budgets is being made to permit a paleoclimatic interpretation of deep core records. The results indicate the need for a revision of the isotope "thermometry" for application in the tropics. However, the seasonality of the beta radioactivity, microparticle content, and isotope ratios offers the prospect of a mass balance chronology. This is important in that precipitation is believed to be a more indicative paleoclimatic parameter than temperature in the tropics.