In a study of uncomplicated patients following major long-bone fracture, plasma free fatty acid levels were found to be statistically significantly higher in those with multiple injury within 12 hours of injury. Arterial oxygen tension was significantly lower in these patients 12 and 24 hours postinjury. A strong positive correlation was found between high FFA and low arterial oxygen tensions in all cases up to 24 hours after injury. The implications of these findings in relation to fat embolism (or post-traumatic) syndrome are discussed.