Ensuring that people have the appropriate level of numeracy skills is particularly important in jobs which involve a risk to public safety and the environment. This research investigates the job-related numeracy requirements in the chemical spraying and handling operations of the horticulture, local government, outdoor recreation and warehousing industries. Findings from this study indicate that the worksite influences both the type of numeracy skills needed as well as how they are deployed. Numeracy in the workplace differs from formal, rule-based abstract mathematics taught in school and requires training that is relevant to the specific applications of the skill. Implications for the future practice of teaching numeracy on the job are offered and highlight the need to consciously develop critical thinking, learning-to-learn, planning and problem-solving skills in workers. (Contains 1 figure and 3 tables.) [This report is part of the Adult Literacy National Project, funded by the Australian Government through the Department of Education, Science and Training. For "Learning Numeracy on the Job: A Case Study of Chemical Handling and Spraying. Support Document," see ED494051.]