AbstractThis paper reviews information on the composition of the microbial phosphorus pool and the current approaches used to quantify the amount of phosphorus held in the soil microbial biomass. Data were compared on microbial phosphorus concentrations in soils under different land use systems (grasslands and forested lands) and agricultural practices, and the sources and extent of variation in the reported values are discussed. Information is also given of phosphorus flux and turnover through the soil microbial biomass, including the process regulating these values, with emphasis on immobilization and mineralization.