Participatory (collaborative, multiparty, citizen, volunteer) monitoring is a process that has been increasing in popularity and use in both developing and industrialized societies over the last several decades. It reflects the understanding that natural resource decisions are more effective and less controversial when stakeholders who have an interest in the results are involved in the process. An adequate number of such projects have now been organized, tried, and evaluated such that sufficient information exists to recommend a comprehensive approach to implementing such processes. This handbook was written for managers and scientists in the United States who are contemplating a participatory approach to monitoring biological resources, especially biodiversity. It is designed as a how-to manual with discussions of relevant topics, checklists of important considerations to address, and resources for further information. Worksheets for developing, implementing, and evaluating a monitoring plan are posted on a companion Web site. The subject matter is divided into 3 stages of a monitoring project encompassing a total of 22 topical modules. These modules can be used in any sequence on an ongoing basis. Stages and modules include (1) planning documentation, goals, indicators, collaboration, decisions, context, organization, participants, communication, incentives, design, and resources; (2) implementation training, safety, fieldwork, sampling, data, and quality; and (3) follow through analysis, reporting, evaluation, and celebrations. Collaboration always involves colearning, so documenting choices, plans, and activities with the Web site worksheets is integral to the manual's effectiveness.