This article undertakes an empirical investigation of the determinants of voluntary adoption of the ISO 14001 environmental management system by French farmers. The adoption model incorporates the expected profitability of implementing the standard and investigates the impact of prior knowledge on the probability of adopting. Two information measures are considered: a “reported information” indicator and an “estimated knowledge” score. The probit parameter estimates reveal that, while the expected profitability of implementing the standard is a significant determinant of adoption, real and perceive prior knowledge measures play a significant but potentially counterintuitive role.