An ultrasonographic unit (A-scan mode) has been evaluated as a noninvasive method for estimating body fat in 25 dogs. Six anatomical sites were defined and subcutaneous fat thickness was measured by means of ultrasound and histology. Total body fat was subsequently calculated in 12 dogs. There was a high correlation between histology and ultrasound for the measurement of subcutaneous fat (r = 0.81; P less than 0.001). Total body fat was successfully predicted using measurements taken with ultrasound at the lumbar area (r = 0.87; P less than 0.001). Measurements of subcutaneous fat thickness from other anatomical sites did not estimate body fat with the same accuracy. These results suggest that ultrasound can reliably measure subcutaneous fat in dogs and that these measurements, when taken from the mid lumbar area, can be used to predict total body fat.