Singular spectrum analysis (SAA), a variant of principal component analysis, is applied to a time series of the Southern Oscillaton index (SOI). The analysis filters out variability unrelated to the Southern Oscillation and separates the high-frequency, 2- to 3-year variability, including the quasi-biennial oscillation, from the lower-frequency 4- to 6-year El Ni¿o cycle. The maximum entropy method (MEM) is applied to forecasting the prefiltered SOI. Prediction based on MEM-associated autoregressive models has useful skill for 30--36 months. A 1993--1994 La Ni¿a event is predicted based on data through February 1992. ¿ American Geophysical Union 1992