Sea surface temperature (SST) data from the Scanning Multichannel Microwave Radiometer (SMMR) for the entire SEASAT mission (July 6 to October 10, 1978), was obtained from the SEASAT project office and has been analyzed for the mid-latitude North Pacific (20¿N--50¿N, 145¿E--130¿W), and the eastern tropical Pacific (10¿S--20¿N, 95¿W--145¿W). Systematic cross-scan SST biases were observed in the SMMR data, strongly dependent upon latitude, solar elevation, time of day, and month. The cross-scan biases are ascribed to incomplete accounting for Faraday rotation of polarized microwave energy propagating upward through the ionosphere. A second systematic SST bias occurred between data of ascending and descending passes nearly 12 hours apart. The bias increased steadily through the mission as the SEASAT orbit moved from 6 A.M./P.M. to 12 A.M./P.M. local sun time coverage. The ascending/descending bias is ascribed to measurements being made at different times in the diurnal cycle of SST. Corrections for the two systematic effects were derived and applied to the SMMR data to produce maps of SST. In mid-latitude, 10 and 30 day maps of SMMR SST were compared with similar maps produced from routine shipboard SST observations (mostly engine injection temperatures). The monthly SMMR and shipbased maps agreed at the 0.5--0.7¿C rms level in July and September, but exhibited a 0.5¿C rms scatter about a significant 1.0¿C bias in August. The August bias may be a reflection of true mid-summer vertical differences in temperature between the 1 cm depth of SMMR observations and the typically 5 m depth of ship observations. Mostly SST anomalies (deviation from climatology) for SMMR and ship exhibited similar patterns, but the SMMR maps appear superior because of their better spatial data coverage. In the eastern tropical Pacific, a sequence of 15 8-day interval maps were constructed. The maps reproduce known climatological features, in particular the cold tongue of water along the equator. Week-to-week variations occur in the intensity of the cold tongue. In addition, wave-like patterns occur along the meridional gradient just north of the equator, having ~1000 km wavelength, and propagating west at about 42 km/day.