The main oceanic fronts of the North Pacific are investigated and the principal frontogenetic processesdescribed. Fronts are features of the upper ocean and occur near mass transport and energy flux convergencezones. Frontogenesis in the upper layers of the ocean is strongly dependent upon the configuration of thewind stress field. Temperature and salinity fronts in the upper ocean are not necessarily coincident, nor arethey always accompanied by density fronts. During periods of strong and persistent winds, the upper andlower portions of the front may separate at pycnocline depth by as much as 200 km, suggesting Ekman-typedisplacement of the upper layer. Multiple temperature and salinity fronts, spaced 60-70 km apart andsuggestive oi baroclinic Rossby waves, are observed off northeastern Japan at the confluence ol the Kurosniowith the Oyashio. Not all temperature and salinity fronts are accompanied by strong baroclinic flow and themaximum baroclinic flow often occurs several kilometers distant from the surface manifestation of thesefronts.