This study evaluates the interdecadal variability of El Nino/Southern Oscillation (ENSO) in 21 coupled general circulation models (CGCMs) participating in the Inter-governmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). 110 years of the Climate of the 20^th Century (20C3M) simulations are analyzed using wavelet analysis. The results show that the state-of-the-art CGCMs display a wide range of skill in simulating the interdecadal variability of ENSO. The 21 models can be categorized into three groups. The first group (8 models) shows an oscillation with a constant period shorter than the observed ENSO period, and sometimes with a constant amplitude. The second group (5 models) does not produce many statistically significant peaks in the ENSO frequency band, but usually produces one or two prominent peaks (episodes) at period longer than 6 years. The third group (8 models) displays significant interdecadal variability of ENSO in both amplitude and period. Among them, only the MPI model reproduces the observed eastward shift of the westerly anomalies in the low-frequency regime.