Chlorpyrifos, an organophosphate pesticide moderately toxic to humans via inhalation and dermal absorption (LD50 oral, rat = 226 mg kg-1, LD50 skin, rabbits = 1265 mg kg-1), is widely used to eradicate termites in Australia. A series of 28 surveys totaling 32 separate assessments, or 10% of all professional users in Perth, Western Australia, comprised biological monitoring, exposure assessment techniques, a health symptoms and work practices questionnaire. Chlorpyrifos metabolite 3,5,6-trichloro-2-pyridinol and alkyl phosphates were extracted from urine, and serum cholinesterase (SChE) and erythrocyte acetylcholinesterase from blood. Chlorpyrifos was extracted from 24 patches removed from a supplied cotton overall, cotton gloves worn under protective gloves, 7 absorbent patches placed on the skin and an organic vapour collection tube. Surface wipes were collected in the workers vehicle and on the workers forehead. Chlorpyrifos was applied in either 0.5% (n=2) or 1% (n=26) concentration of active ingredient in water solution. Surveys took place at pre-construction sites (n=5) where pesticide was sprayed onto a prepared site, existing buildings with concrete foundations (n=17) where pesticide was injected under pressure around the perimeter of the building and existing buildings with suspended floors requiring the worker to spray under floor (n=6). Combined left and right glove deposition was 9 mg hour- 1 (SD = 18 mg.hour-1). Mean deposition on overalls was 14 mg.hour-1 (SD = 12 mg.hour-1), on skin patches was 0.2 ƒÝg.cm-1.hour-1, on vehicle gear-stick was 3 ƒÝg (SD = 8 ƒÝg) and, on steering wheels¡¦ was 3 ƒÝg (SD = 3 ƒÝg). The mean protection 4 factor of overalls, a ratio of outer layer and inner levels, was 75 (SD = 411). Mean air concentration of chlorpyrifos during an application was 30 ƒÝg m-3, and 17 ƒÝg m-3 8 hour TWA (SD = 40 ƒÝg m-3 8 hour TWA), and in one group of 17 workers correlated (p<0.05) with ambient air temperature (15 to 38 oC). Urinary metabolites and SChE activity were effective indicators of exposure. The health symptoms questionnaire did not highlight significant health effects. A discrepancy between operators¡¦ perception of risk and their actual exposure requires addressing, for example the measured high deposition rate to hands was ineffectively controlled, as 48% or workers wore inappropriate or no gloves and only 26% washed their hands after completing their tasks. All workers indicated in the questionnaire they would wash their hands after completing their tasks. The questionnaire also highlighted a high incidence of poor work practices, 58% spilt the concentrate at least once a week, 74% had recently spilt/splashed diluted chlorpyrifos in their eyes and 90% on their boots, and 52% believed they would benefit from more education concerning chlorpyrifos. Observations concluded that workers unnecessarily increased their exposure by poor work practice. Recommendations include modification to pesticide worker education, licencing and health surveillance systems; an improvement in the understanding of the benefits of a health and safety management systems for employers, and pesticide suppliers taking a stewardship role in the usage of their products.