Little is known about the interaction of ultrasonic liposculpture with fat tissue. The surgical technique is well established and its clinical effects are satisfactory. However, the in vivo effects on adipose tissue remain to be determined. Previous studies have shown that ultrasound waves break fat cells. The purpose of this study was to ascertain whether ultrasound waves can cause the release of fatty acids from the molecular structure of triglycerides. A double-blind study was designed with samples obtained from traditional and ultrasonic liposuction of an equivalent area in the same patient. Samples were checked for triglycerides and for free fatty acids. Triglyceride values were always higher in the sample that had undergone ultrasonic procedure. No significant differences were observed between the free fatty acid chromatograms of the two kinds of samples analyzed. Data showed that no changes occurred in the triglyceride molecule when using ultrasound waves in the experimental conditions.