Blood samples for determination of plasma free fatty acids were obtained throughout the night by means of an indwelling catheter. The first sample was drawn at the onset of rapid eye movements and a second after 15 minutes of these movements. Subjects were then awakened and asked to relate their dreams; a third sample was drawn 15 to 25 minutes later. Anxiety scores derived from 20 dreams of nine subjects had significant positive correlations with changes in free fatty acids occurring during REM sleep. No statistically significant relation was found between anxiety and the changes in free fatty acids occurring from the time just before awakening to 15 to 25 minutes later. Presumably, anxiety in dreams triggers the release of catecholamines into the circulation, and these catecholamines mobilize proportional amounts of free fatty acids from body fat.