OBJECTIVE:We studied the validity and reproducibility of a new abdominal ultrasound protocol for the assessment of intraabdominal adipose tissue. MEASUREMENTS: Intra-abdominal adipose tissue was assessed by CT, MRI, anthropometry and ultrasonography on a single day. By ultrasonography the distance between peritoneum and lumbar spine was measured using a strict protocol, including the location of the measurements, pressure on the transducer and respiration. All measurements were repeated after 3 months. RESULTS: The study population consisted of 19 overweight patients with a body mass index (BMI) of 32.9 kg=m 2 (s.d. 3.7), intra-abdominal adipose tissue on CT 140.1 cm 2 (s.d. 55.9), and a mean ultrasound distance of 9.8 cm (s.d. 2.5). There was a strong association between the CT and ultrasonographic measures: Pearson correlation coefficient was 0.81 (P < 0.001). The correlation between ultrasound and waist circumference was 0.74 (P < 0.001), the correlation between CT and waist circumference was 0.57 (P ¼ 0.01). Ultrasound appeared a good method to diagnose intra-abdominal obesity: the area under the ROC curve was 0.98. During the follow-up period of 3 months, the patients lost on average almost 3 kg of body weight. The correlation coefficient between changes in intra-abdominal adipose tissue assessed by CT and ultrasound was 0.74 (P < 0.001). The correlation coefficient of the mean ultrasound distance assessed by two different sonographers at baseline was 0.94 (P < 0.001), the mean difference 0.4 cm (s.d. 0.9), and the coefficient of variation 5.4%, indicating good reproducibility of the ultrasound measurements. CONCLUSIONS: The results of this validation study show that abdominal ultrasound, using a strict protocol, is a reliable and reproducible method to assess the amount of intra-abdominal adipose tissue and to diagnose intra-abdominal obesity.