Interest is growing in non-invasive diagnostic methods for nails in dermatological pathology. Currently, nail disease diagnosis is based mostly on clinical evaluation; instrumental examination, traditionally, has been performed by magnetic resonance. Ultrasound (US) can be proposed as an easier and more available method for the study of the nail apparatus. In this study, the nail unit normal ultrasound anatomy was investigated to obtain data on adult normal parameters. On 35 healthy volunteers (20 women and 15 men--average age of 27 years) we performed an ultrasonographic study on the nail plate (dorsal and ventral), nail matrix and nail bed of all fingers of the hands using a 18 MHz linear transducer with Esaote Mylab 50. A thick gel layer allowed for appropriate transmission of ultrasound without any additional device. Macroscopic nail features were studied by clinical examination and photographic analysis. The following ultrasound parameters were investigated: nail thickness; nail bed thickness; matrix lenght; matrix-bone distance. Blood flow was studied with the use of colour and power colour Doppler. The nail apparatus echographic anatomy consists in: (a) nail plate, represented by two hyperechoic bands (dorsal and ventral) with an hypoechoic or anechoic space between them; (b) nail bed, represented by an area of dys-homogeneous hypo-echogeneity; (c) nail matrix, represented by a markedly hypoechoic area corresponding to the region under the nail sulcus; (d) ligaments, sometimes well detectable and formed by a specialized connective tissue; and (e) vessels, well evaluable through doppler examination.