Although the topography of the isthmus of parotid gland and facial nerve is of greatimportance in surgery, yet there is a lot of disagreements among its descriptions in thetextbooks and literatures. In order to clarify this discrepancy, 100 sides of the parotidgland of adult cadavers were dissected and studied. The isthmus of parotid gland was present in all of our specimens, but its shape,number and location were subjected to a number of variations. Its number varied 1--7.the common one being 3 or 4. The most common location of the isthmus was in thegap between the temporo-facial and cervico-facial divisions of the facial nerve (94.6%).The less frequent occurrences were: in the gaps of the branches of the temporo-facialdivision (58.1%), both above and below the trunk of the nerve (43%), in the gapsof the branches of the cervico-facial division (27.9%), at the posterior border of thedeep lobe, immediately below the trunk of the nerve(16.1%) and the least common onewas above the trunk of the nerve (only 5.4%). According to the numbers of division of the nerve, we classified the facial nerve into4 types. Type Ⅰ is the normal pattern (93%) in which the facial nerve, as soon asit emerges between the superficial and deep part of the parotid gland, divides into 2divisions and then is further divided into 5 branches. Type Ⅱ consists of 4% in theseries in which the primary division of the facial nerve is 3 in number. In the type Ⅲ(2 cases only), the facial nerve after piercing into the parotid gland continues to runforward as a single trunk for a short distance. Type Ⅳ is the only case in which theprimary division of the facial nerve is 4 in number. In 41 out of 93 sides, there are a few branches piercing the substance of theisthmus. In our specimen, the majority of posterior facial vein are lying between the super-ficial and deep lobes of the parotid gland.