Robert Spear is a Professor in the School of Public Health, University of California and is an engineer by training. His research interests focus on the assessment and quantification of human exposures to toxic and infectious agents in the environment. His early work concerned the exposure of agricultural workers to pesticides. In recent years his research has concerned the use of mathematical and statistical techniques in the assessment and control of exposures to both chemical and biological agents. His current work is in collaboration with colleagues both at Berkeley and at the Sichuan Institute of Parasitic Disease in China focused on determinants of the incidence and control of the parasitic disease schistosomiasis. The innovative aspects of this work relate to the integration of traditional epidemiological field data, utilizing geographic information system technology, with that available from both high and low resolution remotely sensed data. Both sources of data are integrated through mathematical models that allow both tracking and forecasting of disease intensity over time. Recent work has focused on the internal potential of villages to sustain disease transmissions and spatial inter-connectedness of the transmission process between villages.