Some recent hypotheses for the El Ni¿o--Southern Oscillation (ENSO) imply that fluctuations of the Mindanao Current may be involved in the early stages of the phenomenon. In this paper, first the relatively sparse knowledge of this southward flowing western boundary current is reviewed, and then the difference in sea level between the islands of Mindanao in the Phillipines and Malakal in Palau is used as an index of Mindanao Current fluctuations. The difference series spans the period 1974 through 1985, encompassing the 1976 and 1982--1983 ENSO events. In addition, the somewhat anomalous (but non-ENSO) 1980 year is included in the record. The dominant signal in the sea level difference is a biannual oscillation. Estimated transport changes are at least 16 Sv, or about 50% of the mean transport. In the year prior to two ENSO events, the Mindanao Current is relatively weak, while during the ENSO year the current is stronger than average. However, the strongest fluctuations occur in the non-ENSO period 1979--1980, and thre is no apparent relationship between the fluctuations of the Mindanao Current and the strength of the ENSO signal. ¿ American Geophysical Union 1988