In the Western Equatorial Pacific Ocean a coastal undercurrent lying within 40 km of the east coast of New Ireland was in May 1988 found to be transporting high-salinity, low dissolved oxygen, high-nutrient thermocline waters northwestwards towards the equator. Acoustic doppler current profiler measurements showed the peak alongshore current speeds of approximately 60 cm s−1 occurred at 235 m depth and the volume transport between the 24.5 and 26.5 kg m3 isopycnals (approximately 176 to 320 m) was 2.0±0.1×106 m3 s−1. We suggest that this current be called the New Ireland Coastal Undercurrent (NICU). Just to the east of 149°E, the NICU was diverted to the north and forced to interact with the Equatorial Undercurrent (EUC). Transport budgets in the region bounded by 149°E, 153°E, 2°S and the equator, between the 24.5 and 26.5 kg m−3 isopycnals show that approximately 5×106 m3 s−1 of water originating from east of New Ireland, including the NICU was added to the EUC system. This accounted for approximately half of the southern hemisphere thermocline waters in the EUC system at 153°E.