Pesticides are extensively used in agriculture and numerous chemical active ingredients and product formulations have been marketed since the 1950ies. Human populations can be exposed to pesticides via multiple routes, such as application of these substances in occupational settings, or via pesticides migrating into the (home) environment following agricultural pesticide applications in vicinity. Pesticide exposure has been associated with different health effects, such as Parkinson’s Disease (PD). Evidence for the role of specific active ingredients is still limited, however, as the wide range of pesticides used over time and space complicates accurate assessment of exposure. It is also not clear to what extent epidemiological findings obtained abroad are relevant for the Netherlands. The first aim of this thesis was to develop and apply improved methods for the assessment of occupational and environmental pesticide exposures in several retrospective epidemiological studies. The second aim was to investigate the association between pesticide exposures and PD in the Netherlands. The work described in this thesis has resulted in country-specific crop-exposure-matrices and a spatio-temporal model to assess environmental pesticide exposure at the residential address for the Netherlands. These methods address pesticide exposure at the level of active ingredients, while going back in time for several decades. Low specificity and high correlations between pesticide exposures remained an issue that cannot be easily solved however. In part this is inherent to pesticide applications, with several active ingredients being applied during the same time window and/or location. But also the exposure assessment methods have their limitations. High correlations limit the ability to distinguish effects of individual pesticides on health in epidemiological studies. Further improvements will require additional data collection, such as higher (spatial and temporal) resolution data on crop cultivation and pesticide use, for time ...