The alkenone unsaturation index (U (super K') (sub 37) )is used to reconstruct Eocene and Oligocene sea surface temperatures (SST) at eight DSDP sites (253, 336, 356, 357, 367, 51l, 593, and 612) from high-, mid-, and low-latitudes of the North and South Atlantic. Alkenone distributions indicate that SST of high latitudes during the early late Eocene were as high as 17 degrees C and 18 degrees C, respectively, and by the middle Oligocene SST at these locations had decreased to 9 degrees C and 14 degrees C. However, mid-latitude SST in the southern Atlantic decreased only slightly from a minimum of 28 degrees C to 26 degrees C. Furthermore, we speculate that the general absence of methyl-C (sub 38:3) alkenones, indicates a change in the biosynthetic pathways of alkenone-producing organisms since the Eocene; however, this change is assumed not to have an effect on temperature calibration. A comparison of our results to oxygen isotope studies indicates that U (super K) (sub 37) is indeed a valid approach to determining SST as far back as the early Eocene and should be considered a reliable independent technique for such investigations.