Flows at subtidal frequencies are resolved from 20 months of current observations at multiple sites across the narrows of Cook Strait, New Zealand. The substantial tidal flows (spring tides .3 m s 21 ) are challenging to measure with moored ADCPs. Along-strait residual flows are on the order of 0.05-0.1 m s 21 , but there were differences across the strait and also through the annual cycle. The calculated net residual transport is 20.25 Sverdrups (Sv; 1 Sv [ 10 6 m 3 s 21 ) (i.e., negative sign

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... implies to the south, from Tasman Sea to Pacific Ocean). This is smaller (by a factor of 2-3) than that estimated from previous sparse current measurements. Crucially, however, these new data also suggest that, over the austral summer-autumn period, there is persistent residual flow northward on the western side of the strait so that the summer-autumn net 20.15-Sv flow can be separated into 10.065-Sv westside and 20. 22-Sv eastside flow. This western northward flow had a seasonal bias, appearing only in the summer-autumn period. The observations also show persistent temperature stratification on the order of 28C over the full depth of the water column in this late summer-autumn period. An implication is that there is vertical shear influencing the residual flow estimates. A range of exchange flow scenarios are considered with the most extreme indicating that the flow on the western side of the strait in the January-June period might be as much as 10.08 Sv northward. This has substantial implications for regional circulation as well as for the nutrient supply for the nearby Marlborough Sounds.