Although commonly reported in marine and freshwater environments, little is known about the biological sources of long chain alkyl 1,13- and 1,15-diols, and factors controlling their distributions. Here we analyzed the occurrence and distribution of these lipids in a comprehensive set of marine surface sediments and compare their distributions with environmental conditions like sea surface temperature (SST), salinity and nutrient concentrations. Fractional abundances of the C 28 1,13-, C 30 1,13- and C 30 1,15-diols show a strong correlation with SST and based on these results, we propose the Long chain Diol Index (LDI), which expresses the C 30 1,15-diol abundance relative to those of C 28 1,13-, C 30 1,13- and C 30 1,15-diols. The LDI shows a strong linear correlation with SST (LDI=0.033×SST+0.095; R 2=0.969, n=162) over a temperature range of -3 to 27°C. Long chain diol distributions in sediments from the South Atlantic close to the Congo River outflow (West Africa) provided a 43kyr LDI SST record. This record reflects several known climatic events and shows similarities with an alkenone-derived SST record obtained using the same suite of sediments, both in trend and in terms of absolute SST. This confirms the potential of the LDI as a proxy for palaeo-SST reconstruction. © 2012 Elsevier Ltd.