A rigorous analysis of tide records from Puerto Princesa on Palawan Island in the Philippines demonstrates that the harbor's fortnightly varying seiche activity is coherent with the cycle of springneap tides in the Sulu Sea and lags it by 2.9 days. This delay closely matches the time required for the formation and travel of tide-generated internal solitary waves northwestward across the Sulu Sea and strongly supports the hypothesis that coastal seiches can derive their energy from the tide-producing forces by way of tidal currents and internal waves. However, the analysis also indicates that the quantity of energy transferred from the tide to the seiches has a pronounced seasonal variability which may be related to seasonal variations in wind stress. It is unlikely that accurate predictions of tide-produced seiches will be possible without a sound theoretical understanding of the mechanisms by which energy is transferred to them by deep-sea internal waves. ¿American Geophysical Union 1987