Results of an investigation of the nature of the mesoscale variability of sea surface temperature (SST) inthe upwelling zone off the central coast of Oregon are presented. A knowledge of SST mesoscale variability isimportant toward understanding the mesoscale air-sea interaction process in an upwelling zone. Almost-daily sea surface temperature data gathered by remote sensing techniques provided the basis for this investi-gation. These data were gathered over a period of 60 days during the COHO Project in summer 1973. In order to study the influence of wind forcing on the mesoscale SST field, wind data were gathered from ananemometer located at Newport, Ore. Some important results of this investigation are: 1) the daily SST fields respond rapidly to wind forcing;2) the three-week mean SST's tend to follow the large-scale bathymetry; and 3) identification of SST eddiesfrom day to day on daily perturbation (from the three-week means) maps is made difficult because of theexistence of strong horizontal flow and strong shear in the longshore current. Other important results are revealed by a two-dimensional spectral analysis of the daily horizontal sea surface temperature fields and theperturbation fields. This analysis indicates that a large amount of variance of the sea surface temperatureis concentrated in the 16-40 km wavelength range, and over the range of scales from 4-20 km the isotropicpart of the temperature variance spectrum obeys a 3 power law. These spectral results are importantbiologically and physically. An interesting feature of the mesoscale SST field, which is also important biologically and physically, is the existence of strong horizontal SST gradients called "oceanic fronts."