Background：Dermatologic patients need advice on how much ointment or cream to apply, in particular topical corticosteroids. The instructions given to patients concerning topical therapy are frequently vague. Objective：The aims of this study are to make simple guidelines on the topical application of ointments or creams for patients, parents, doctors and nurses, and to check the accuracy of these guidelines in practice. Methods：The average height and weight according to the different age groups and sex were measured from Korean standard growth and developement chart. From this chart, their total body surface areas(BSA) were calculated using a standard nomogram. The length of the tips of their index fingers was measured; measuring from the distal skin-crease to the end of the finger. One finger-tip unit(FTU) was defined as the amount of ointment expressed from a tube nozzle with a 5 ㎜ in diameter, covering from the distal skin-crease to the tip of the palmar aspect of the index finger. The average area of abdominal skin covered by one finger-tip unit, and that of one palm were measured by computer scanner(Hurapack scanner, 4C) and image analyzed program(Image Pro. Plus V. 3.0, Micromedical). Each patient then placed his or her right hand lightly, palm side down with the fingers and thumb closed, onto Hurapack scanner 4C. A tracing of the outer edge of the hand was made from the ulnar to radial styloid by photoshop program. The outlined area and enclosed area were measured by an image analyzer. Results 1. The average length of each finger-tip was 2.48±0.2㎝ in males and 2.24±0.13㎝ in females. 2. The average weight of one FTU was 0.46±0.03g in males and 0.40±0.02g in females. 3. The average area of palm was 145±12.4㎠ in males and 115.9±10.1㎠ in females. 4. The average area of abdominal skin covered by one FTU was 278±34.4㎠; The average area was 303±24.3㎠ in males and 253±21.9㎠ in females. (Korean J Dermatol 2000;38(12)：1624~1629) 5. The number of FTU of adult male required to treat various anatomical sites was : face and neck, 2.6; trunk and buttock, 10.5; arm and hand, 5; leg and foot, 10. The number of FTU of adult female was : face and neck, 2.8; trunk and buttock, 11; arm and hand, 5.5; leg and foot 11. 6. The number of FTU of children required to treat each anatomical site was variable because of differential growth according to different age. Conclusion：The concept of FTU provides convenient means of rapidly assessing the approximate amount of ointment or cream required for the treatment of patients.