A study was conducted to determine mixer/applicator exposures and doses to Garlon-4 (64700567) herbicide during directed foliar application when using backpack sprayers for herbicide application. Worker exposures during the mixing and directed foliar application of the herbicide were monitored environmentally and biologically. Measurements of herbicide concentrations were taken from air samples, body surface deposition from patch and skin wash samples, and urine samples. Patch and air extracts were analyzed by gas chromatography; hand wash samples were analyzed by reverse phase high performance liquid chromatography; and urinary levels of the triclopyr (55335063) were measured by gas chromatography/mass spectrometry. Opportunities for exposure arose among the applicators during handling of the concentrate and during preparation and application of the spray mixture. The potential for exposure via inhalation was low due to the relatively low vapor pressure of Garlon-4. Several work practices and procedures potentially affecting exposure were tracked for each worker. Several factors appeared to influence exposure and doses to triclopyr including the height and density of vegetation, training and experience, use of gloves, mixing procedures, and equipment maintenance. Recommendations are offered which suggest that the sites chosen for application have vegetation which does not exceed 6 feet in height, that all workers applying pesticides and crew leaders be thoroughly and formally trained in the goals of herbicide application and procedures for mixing and application, that operations and maintenance plans for spray equipment be developed and implemented, that personal protective equipment be worn during mixing and application, and that personal hygiene be stressed for workers who apply pesticides.