The study of body composition is becoming increasingly important in the field of nutritional medicine. The possibility of assessing body composition easily and economically has therefore raised considerable interest. Using straightforward correlations, we have compared the data obtained from the assessment of BF% using plicometry, impedance analysis and the interactivity of close-infrared rays; in addition, we studied the possible influence of the distribution of fatty tissue, expressed as W/H, on the results obtained using these methods. One hundred and forty-eight subjects (51 M and 97 F) were studied aged between 13 and 76 years old, with BMI ranging between 16.8 and 56.4; subjects were divided into three groups according to BMI and W/H. The three methods proved to be well correlated in patients with BMI less than 30 (r between 0.92 and 0.74), whereas correlations were less marked and less significant in groups with BMI greater than 30. W/H seemed capable of influencing results obtained using these methods and this was more evident in results obtained using impedance analysis (p less than 0.0001). The three methods studied were comparable in normal weight and slightly overweight patients, whereas contrasting findings were obtained in patients with moderate and severe obesity. Extreme caution must therefore be used in interpreting the data obtained in these subjects.