Abstract: The handheld data-logging spray apparatus incorporates a global positioning system (GPS) receiver and microcontroller into a conventional handheld spray unit. As an operator dispenses a chemical using the handheld data-logging spray apparatus, the microcontroller records (among other things) the volume of chemical dispensed and the GPS location of the sprayer. The recorded data is processed and stored on a removable USB thumb drive. The operator can download the data from the thumb drive and manipulate the data using a conventional spreadsheet program or a commercially-available geographic information system program.