PURPOSE:To measure the thickness of adductor pollicis muscle in healthy adults. This measurement will be used as a nutritional anthropometric parameter in further studies. SUBJECTS AND METHOD:Four hundred and twenty-one healthy adults were studied, 209 men and 212 women, with ages ranging from 18 to 87 years, living in Rio de Janeiro.The adductor pollicis muscle was also studied in the human anatomy lab as well as in normal healthy volunteers using CAT scans and nuclear magnetic resonance imaging to ensure that only the adductor pollicis was included in measurement of muscle thickness with a Lange caliper.To standardize the measurement, the methodology was detailed, with subjects sitting with the dominant hand dangling over the homolateral thigh and the elbow bent at approximately a 90° angle. The Lange caliper was applied at a pressure of 10 g/mm 2 , pinching the adductor pollicis muscle at the vertex of an imaginary angle between the thumb and the index finger. The average of 3 consecutive measurements was considered to be the muscle thickness.RESULTS: This study provides the first estimates of adductor pollicis thickness in normal healthy subjects as an anthropometric parameter. The normal values in the dominant hand for men were 12.5 ± 2.8 mm (mean ± SD), median 12 mm, and for women were 10.5 ± 2.3 mm, median 10 mm.