Interdecadal variations in the early (May--June) summer monsoon rainfall over South China (SCMR) are found to be related to the ENSO (El Ni¿o/Southern Oscillation) and the PDO (Pacific Decadal Oscillation). An interdecadal variation in SCMR can be identified, with more dry (wet) monsoon years during the periods of high (low) PDO index. Such variations are also related to ENSO in association with PDO. When ENSO and PDO are in phase, i.e. high PDO phase/El Ni¿o events, or low PDO phase/La Ni¿a events, the SCMR tends to be below or above normal respectively more often. But when the ENSO and PDO are out-of-phase, the SCMR has no wet or dry preference. Such relationships appear to be related to the intensity of the subtropical high determined by the superposition of the effects of ENSO and PDO.