Recent validation studies have confirmed that the first along-track scanning radiometer (ATSR) can retrieve sea surface temperature (SST) to an accuracy of 0.3 K even in the presence of heavy atmospheric aerosol. However, using the standard (pre-launch) retrieval, this accuracy is achieved only when data from all three thermal channels (3.7, 11 and 12 &mgr;m) are available; in the absence of 3.7 &mgr;m data, retrieved SSTs are subject to significant cold bias. As 3.7 &mgr;m data are useful only for nighttime observations, and ATSR's 3.7 &mgr;m channel failed in May 1992, only 11 and 12 &mgr;m data informed SST derivation for most of the 1991--1996 mission. We demonstrate the potential for improvement in this retrieval, based on comparison of observed brightness temperatures with precise SSTs derived using 3.7 &mgr;m data. A reduction in global-mean cold bias from >0.6 K to <0.1 K is achieved, with standard deviation approximately halved. We also examine the treatment of optical pathlength variation around the ATSR swath. ¿ 1998 American Geophysical Union