Transverse furrows, or Beau's lines, were noted in the fingernails of all 6 divers following a deep saturation dive to apressure equal to 1100 feet (335 meters) ofsea water (3,370 kPa), and in 2 of6 divers following a similar dive to 1000 feet (305 meters) of sea water (3,164 kPa). Both dives took place at the Ocean Simulation Facility of the Navy Experimental Diving Unit in Panama City, Florida. The divers breathed a partial pressure of 0.40 - 0.44 atm abs (40.5 - 44.6 kPa) oxygen, with the balance helium, during most of the time under pressure. All divers performed hard work on bicycle ergometers during the dives. Four of the divers on the first dive were treated during the dive for pain-only decompression sickness. Beau's lines have been reported in numerous medical conditions such as typhus, rheumatic fever, malaria, myocardial infarction, and other severe metabolic stresses. To the author's knowledge this is the first report of Beau's lines associated with saturation diving.