Data from the Surveyor 1968 Spring cruise were used to study the vertical distribution of salinity, temperature, dissolved oxygen, apparent oxygen utilization, pH, alkalinity, specific alkalinity and percent saturation of calcite in two sections, one along 162°W from 35°N to 45°N and the other along 180°W from 35°N to 50°N. Data from this cruise and additional data from the Surveyor 1968 Fall cruise, YALOC 66 cruise (summer) (Barstowetal, 1968) and Boreas cruise (winter, 1966) (SIO reports, 1966) were used to study the distribution of salinity, temperature, apparent oxygen utilization, preformed phosphate and depth on the sigma-t surfaces of 26.8 and 27.3 in an area between 35°N and 52°N and 162°W and 155°E. In both sections the vertical distribution of the physico-chemical parameters is such that in general there is a tendency for the isograms to slope upward from south to north following the same trend of the sigma-t surfaces. This indicates that mixing and advection along the sigma-t surfaces play an important role on the distribution of these parameters. AOU data from YALOC 66 cruise (summer) compared to that from Surveyor 1968 Spring cruise suggest that aeration by mixing, eddy diffusivity and conductivity takes place to more than 500 meters depth at about 50°N. It also suggests that the changes of organic primary production at the euphotic zone during different seasons of the year may affect to a great extent the AOU distribution on the 26.8 sigma-t surface and to a very small extent on the 27.3 sigma-t surface. The direction of flow suggested by the AOU distribution on the 26.8 and 27.3 sigma-t surfaces was compared to that indicated by the acceleration potential contours on the S[subscript t] = 125 cl/ton and S[subscript t] = 80 cl/ton surfaces drawn by Reid (1965). The disagreements were explained in terms of mixing and possible gradients of primary production at the sea surface. On the 26.8 sigma-t surface a southward flow connecting the westward flow south of the Aleutian chain and the eastward flow farther south, between 175°E and 180°W is suggested by the AOU distribution but not by the acceleration potential contours. If the circulation pattern at this density surface is similar to that at the sea surface, this linkage is very likely to be real.