The lumbar part of the sympathetic trunk in 206 sides of cadavers was observed. The results were outlined as follows:1. The average length of the lumbar sympathetic trunk in the adults is 17.58?4.51 cm on the left side and 16.60?5.14 cm on the right side respectively.2. In most cases (40.29?3.42%), there are 4 lumbar sympathetic ganglia on each side. They may fuse with each other between themselves, or the 1st lumbar ganglion fuses with the lowest thoracic ganglion (12.60?2.31%), or the lowest lumbar ganglion fuses with the 1st sacral ganglion (6.31?1.69%).3. The lumbar sympathetic ganglion gives off ramus communicans connecting the corresponding spinal nerve. The number of the ramus communicans of each ganglion varies from 0 to 6, but in most cases, 2～3, and decreases from above downwards along the trunk. There are frequently two or more rami in the upper lumbar ganglia, but only one in the lower ganglia.4. The number and sites of the lumbar ganglia on both sides of an individual are rarely symmetric (1.98?1.37%). One of these ganglia is situated constantly near the brim of pelvis or the common iliac artery, and accordingly it can be found easily.Most of the lumbar arteries are situated deep to the lumbar sympathetic trunk, only in a few cases, they are situated superficially, and all of them occur on the left side. In 25.75?3.05%, the lumbar veins are likewise located superficially. This can be found in any pair of the veins, but frequently at 3rd or 4th ones.The observation may be helpful to surgical operation.