In the páramo ecological belt of the Venezuelan Andes, a long fallow agricultural system is used to produce potatoes and cereals. Total rainfall, surface runoff, soil moisture, drainage, and soil loss were measured in this system during two consecutive years on 10 plots cropped with potatoes and on two successional plots with fallow periods of 1 and 15 years. Total rainfall (1129 mm on average) is characterized by many low-intensity events. The low rainfall intensity and high soil infiltration capacity partly explain the very low runoff (only 1.7% of the rainfall) and the low rates of soil loss (0.58 t/ha/y) on the cultivated plots. The main water outputs were by evapotranspiration (61%) and drainage (37%). The greatest runoff and soil losses were observed at the beginning of the fallow period when the ground cover was scarce; however, after a few months of fallow, both processes decreased below the rates measured on the cultivated plots. Because soil loss was not significant on all study plots, it is suggested that traditional fallow agriculture does not have a negative environmental impact at a local scale.