The South Pacific Convergence Zone (SPCZ) is the most prominent rain feature of the Southern Hemisphere, but is a very understudied region. Changes in the SPCZ can affect freshwater availability to people living on the islands in the South Pacific. The satellite record shows precipitation patterns from the past 37 years; in the tropics the best way to investigate rainfall before 1979 is to examine lake sediment. We used sediment cores with age models from Barora Lake, a shallow freshwater lake in the Solomon Islands, to obtain a detailed view of past rainfall patterns. This lake’s lack of oxygen one meter below the water’s surface has left its sediment in a uniquely undisturbed state. Because of this, and a high accumulation rate, the sediment provides a record of the rainfall in the Solomon Islands over the last millennium. Lipids are well-preserved in sediment over geologic time, making them an ideal proxy for reconstructing tropical paleoclimate. The lipid dinosterol is produced primarily by a limited group of dinoflagellate microalgae and acts as a “molecular fossil”. The isotopic ratio of deuterium to hydrogen (2H/1H) found in dinosterol reflects the 2H/1H ratio in the lake water, which is dictated by changes in precipitation and evaporation. In the tropics, more rain results in 2H-depleted rain and lake water. After purifying dinosterol from the sediment with column chromatography and high-performance liquid chromatography, we found minor fluctuations in the dinosterol 2H/1H ratios, which implies a fairly stable rainfall pattern at this location during the past millennium.