Efforts to elucidate the causes of prostate cancer have met with little success to date and we are still entirely bereft of ways to prevent it. All that is known with certainty is that incidence increases exponentially with age, is higher among men whose father or brother had the disease, and varies by ancestry. Genetics explain a modest portion of familial risk. International comparisons of incidence, temporal trends, social class gradients, and migrant studies strongly suggest that exogenous factors play an important etiological role. Yet the specific factors actually involved, and how they interplay, remain elusive.We conducted in Montreal, Canada a case-control study including about 2000 cases and 2000 controls to investigate the role of environmental factors in prostate cancer risk. The Prostate Cancer & Environment Study (PROtEuS) is set to investigate the role of lifetime occupational exposure to 345 workplace agents, occupational circumstances, spatially-referenced factors, along with lifestyle habits. The seminar will provide an overview of PROtEuS, along with some recent findings in relation to the environment most specifically. An overall trend is emerging suggesting a positive association with traffic-related air pollution, street-level ultrafine particles, and a negative association with residential greenness. These observations appear to be independent of contextual and personal factors, including prostate cancer screening. Others results focusing on workplace exposure to metals will also be presented.