The hazard posed by pesticides in use in Prince Edward Island, Canada, was estimated by a model based on fugacity. Groups of individuals currently working in the field of aquatic toxicology were asked to rank 20 of these pesticides in order of decreasing hazard. There was little agreement between prediction using the model and perceptions of the respondents. There was general agreement between two of the groups of toxicologists surveyed, although this was also variable. The need for standardized methods of hazard assessment is stressed.