Mass balance of Zongo Glacier (Cordillera Real, Bolivia) was reconstructed by using hydrological data. Moreover, the 'linear model' (Lilliboutry) was applied on the balance measurements from Yanamarey and Uruashraju ablation zone (Cordillera Blanca, Peru). Compared with temperature and precipitation data from reliable meteorological stations, these 15-20 yr time series of glacier balances allow us to point out temperature as the principal factor controlling mass balance evolution. Temperature variability strongly depends on ENSO (El Nino Southern Oscillation) events: a clear positive deviation of maxima and minima is generally observed during these events, which strongly increases the ablation. Consequently, a systematical negative mass balance is associated with ENSO events. In Southern Peru and in Bolivia, this tendance is enhanced by a frequent decrease in the precipitation, which modifies the accumulation term at high altitude. So, it is demonstrated that ENSO phenomena closely control the glacier mass balance variability and have a great influence in the rapid glacier retreat observed in this area of Tropical Andes.