Alkenone fluxes in the water column of the Cariaco Basin ranged from 12 to 20 ¿g m-2 d-1 and were inversely related to upwelling strength. The U37K' ratios of sinking particles varied from 0.78 to 0.96 and exhibited seasonal changes that were coherent with a 7¿C variation in sea surface temperature (SST). The correlation between SST and U37K' ratios closely overlapped with the calibration of Prahl et al. <1988>. Alkenone burial fluxes in Cariaco Basin sediments varied markedly over the past ~6000 years, ranging from 0.2 to 5 ¿g m-2 d-1. The U37K' ratios of surface sediments indicate SST was higher (26.3¿C) during the last 50 years of deposition than in the previous 300 years (~25¿C), signaling an upwelling decrease in the latter part of the twentieth century. The lowest U37K'-derived temperatures (~25¿C) were measured in sediments deposited during the little ice age (LIA). These compositions, coupled with relatively low alkenone fluxes (≤2 ¿g m-2 d-1), are consistent with conditions of enhanced upwelling, decreased SST and reduced haptophyte production. The highest U37K'-derived SST estimates (over 26.5¿C) were measured during the Medieval Warm Period (MWP) and suggest reduced upwelling at this time. Prior to the MWP, the alkenone record indicates temperatures of ~26¿C and burial fluxes of ~2 ¿g m-2 d-1. These compositions indicate stronger upwelling conditions during the Holocene relative to the last 50 years and the MWP but annual SSTs above those estimated for the LIA.