Describes the basics of bar-code systems that can be used to maintain inventories or track pesticides, equipment, tree-marking paint, or other materials. Bar codes use a series of vertical black lines and spaces to record data. The standard used to convert data to a bar code is called a symbology. More than 250 symbologies are in use. Forest Service users should consider using symbology code 128, the standard used in the shipping industry. It can encode all 128 ASCII characters (lower-case and capital letters, numbers, punctuation marks, and other symbols) and can be used to create high-, medium-, and low-density bar codes. The label lines are closely spaced in high-density bar codes, allowing more data to be stored, but the label might not be read as reliably. Setup and the initial inventory entry are usually the most time-consuming steps in establishing a bar-code system. A bar code might represent the identification of a container of pesticide. Software, usually some form of database, stores additional information about the container of pesticide, such as when it was purchased, how much the container holds, how much has been used, and when the container was disposed of. The bar code would be placed on the pesticide container when it was received. Each time some of the pesticide was used, a scanner would record the bar code and the user would enter appropriate information about the use. Such a system would allow careful tracking of the use of pesticides and the software would allow the user to prepare periodic reports. This Tech Tip considers three sample uses of bar-code systems by Forest Service employees: tracking tools, inventorying chemicals and material safety data sheets, and reporting on pesticides. An accompanying report, Assembling a Bar-Code Tracking System (0271-2834-MTDC), has more detailed information that can be used to design a bar-code system.