The reef building coral Montastrea annularus was exposed continuously to suspensions of oil and gas-well drilling fluids at concentrations of 0.1 ml/liter, 0.01 ml/liter, and 0.0001 ml/liter in flowing seawater at the U.S. Naval Stage I platform (30 deg 7.5 min N, 85 deg 46.3 min W). After 6 weeks exposure, coral fragments of 12 to 65 sq cm surface area were broken off, rinsed in seawater, and extracted in a one-phase chloroform-methanol-buffer and returned to the laboratory. In the laboratory, the extraction was completed and the phases separated. The lipids were fractionated using silicic acid and thin layer chromatography. Total phospholipid, triglyceride glycerol, total extractable fatty acids, triglyceride fatty acids as well as the wax ester fatty alcohols showed no consistent changes with exposure to the drilling fluids. (Copyright (c) 1984 Springer-Veriag New York Inc.)