Triceps skinfold thickness measured in ten adults aged 19 to 50 yr by a Holtain skinfold caliper, was compared with subcutaneous fat thickness obtained on cross-sections of the left upper arm by computerized axial tomography (CAT). The thickness of subcutaneous fat was measured on CAT scan film directly with the inbuilt computer graphic technique. The measurements taken on CAT scan film were found to be significantly higher (by 21-45%; P less than 0.001) than those by the skinfold calipers. Our findings suggest that skinfold calipers may not be very accurate tools for the assessment of body fat in human beings. Therefore, its use in the determination of body composition, for which great precision is required calls for re-thinking.