The Department of Occupational Health (DST) at the French Institute for Public Health Surveillance (InVS) sought to establish a longitudinal surveillance system designed to improve the epidemiological monitoring of occupational risks: the Coset program (Cohorts for Epidemiological Surveillance Related to Work). The program aims to describe morbidity and its trends in relation to occupational factors across the working population in France. It draws on data from cohorts of current and former workers enrolled in one of the three main Social Security schemes, which cover 95% of the working population in France. It is within this framework that, in close collaboration with the Caisse centrale de la Mutualité sociale agricole (CCMSA), the DST of the InVS planned the recruitment and follow-up of a cohort of individuals randomly selected from among workers affiliated with the Agricultural Scheme at the time of enrollment. Following a preparatory phase aimed at developing the enrollment system and data collection tools, a pilot study was launched in October 2009 to test the system on a limited population prior to its nationwide rollout. This document summarizes the preparatory steps for the study and the various lessons learned from the pilot phase. (R.A.)