The present document, the fourth in the series, is divided into two parts. The first part of this report defines terms used in vegetation sampling, and discusses both the general strategies for sampling vegetation in the Sahel and the specific design of a system for the collection of data in the field to describe and monitor plant communities. Its major concerns are with the sound and practical design of sampling strategies, including stratification of the environment for efficient sampling, site placement, the repeated location of the same sampling point, and the correct selection of the method to be used for sampling from among the many alternatives. A large section is devoted to the selection of parameters for monitoring. The second part examines the results of computer simulations of techniques used for collecting data in the field, including the point centre quadrat, circular plots, and transects.