A finger-tip unit (FTU) is the amount of ointment expressed from a tube with a 5 mm diameter nozzle, applied from the distal skin-crease to the tip of the index finger. Thirty adult-patients treated various anatomical regions using FTU's of ointment. The number of FTU's required was: face and neck 2.5 (s.d. +/- 0.8); front of trunk 6.7 (s.d. +/- 1.7); back of trunk 6.8 (s.d. +/- 1.2); arm and forearm 3.3 (s.d. +/- 1.0); hand 1.2 (s.d. +/- 0.4); leg and thigh 5.8 (s.d. +/- 1.7); foot 1.8 (s.d. +/- 0.6). One FTU covers 286 cm2 (s.d. +/- 80, n = 30). In males one FTU covers 312 cm2 (s.d. +/- 90, n = 16) and in females 257 cm2 (s.d. +/- 55, n = 14). The use of the FTU in dermatological prescribing provides a readily understandable measure for both patients and doctor.