The Department of Occupational Health (DST) at the French Institute for Public Health Surveillance (InVS) has established and coordinates a program to develop exposure-occupational matrix studies for plant protection products tailored to the agricultural population in France: the Matphyto program. This document describes the technical aspects of occupational exposure to arsenic-based pesticides and presents the exposure-occupational matrix studies that have been conducted. Inorganic arsenic is a carcinogen recognized for humans by the IARC (International Agency for Research on Cancer); the main inorganic arsenic derivatives used in agriculture are lead arsenate, calcium arsenate, and sodium arsenite. They act as fungicides and insecticides primarily for three crops: grapevines, potatoes, and fruit trees. Their use was assessed in the matrices from 1945—although their use predates this—through 2001, the year of their total ban.Three exposure indicators (probability, frequency, and intensity) are used to assess the use of arsenic for plant protection in each of these three crops on farms in metropolitan France.These matrices allow for the characterization of phytosanitary exposures based on data that is relatively easy to obtain (type of crops), and using a semi-automated method, ensuring a consistent assessment within a population group. They provide a retrospective and non-differential assessment, provided that the crops on which the subjects worked can be identified. (R.A.)