In August 1992 the R/V Hesperides reoccupied a transatlantic section nominally along 24.5 ¿N previously sampled in April 1957 and in August 1981. Observation of significant warming over the 35-year period has already been reported for the ocean layer between 800 and 2500 m depth (~0.01 ¿C yr-1). We examine decadal-scale variability in the nutrient and O2 measurements primarily comparing the 1981 and 1992 sections. The basin-scale water mass structure remained relatively unchanged from 1981 to 1992. Zonally averaged differences of the chemical data show that the layer of maximum increase in temperature and salinity at 1100 m is roughly coincident with an apparent decrease in O2 concentration of about 7 μmol kg-1. The O2 decrease is equivalent to an average rate of decrease of 0.6 μmol kg-1 yr-1. The vertically integrated water column O2 utilization rate is 0.9 mol m-2 yr-1. This is equivalent to 23--33% of the new production rate estimates in the Sargasso Sea. The O2 decrease at 1100 m cannot be explained by using oxidative ratios relating regeneration of nutrients and O2 consumption. The O2 decrease is not highly correlated with zonally averaged changes in the nutrient measurements. The nutrients show small or insignificant changes near 1100 m over the 11-year period. Part of the O2 decrease might be explained by measurement error (30%) and changes in solubility (20%) due to warming. The chemical changes are likely caused by changes in the characteristics of the source waters entering 24.5 ¿N near 700--1700 m depth. ¿ 1998 American Geophysical Union