Postmortem vitreous humor chemistry studies were reviewed in 25 cases in which death was followed by submersion in fresh water for known lengths of time. The potassium concentrations in cold temperature cases initially increased in a linear manner, but appeared to level off or decline after about 1 week. In hot weather cases, potassium levels rose rapidly during the first few days postmortem. The sodium and chloride levels decreased in a fairly regular fashion, with less temperature variation. Increasing variation in values began to occur at about 7 days. The data show that dilution of the contents of the eye by fresh water begins at about that time in cases of cold water submersion. A formula employing the weighted average of the potassium and chloride concentrations can be used to determine the duration of submersion in cold water over the range of 2-10 days.