Studies of the influence of the El Niño-Southern Oscillation (ENSO) phenomenon on atmospheric conditions of different regions, have determined characteristic trends in rainfall patterns of El Niño and La Niña years. The possibility of anticipating those conditions by using the Southern Oscillation Index (IOS), or other indicators, has created the expectation of using this information for forecasting. An analysis of quarterly and semestral rain information of six localities of Córdoba province, and of the entire region (Zona), verified the inverse association between rain anomaly and the IOS. This relation is more consistent for the warm semester that provides the greater proportion (80%) of annual rainfall in the region. During El Niño years, that correspond to positive rain anomalies, there is a greater frequency of positive anomalies of corn (Zea mays L.) yields, but they are of scarce magnitude. Negative rain anomalies occur predominantly in La Niña years, and are related to negative anomalies of yield, with frequencies statistically different not only to El Niño years, but also to those of Neutral years. Finally, some of the difficulties with the use of ENOS information for forecasting are discussed.