Using wetlands as a sink of nutrients, phosphorus in particular, is becoming an increasingly attractive alternative to conventional wastewater treatment technology. In this paper, we briefly review the mechanism of phosphorus retention in wetlands, as well as previous modeling efforts. A Bayesian method is then proposed for estimating the long-term phosphorus accretion rate in wetlands through a piecewise linear model of outflow phosphorus concentration and phosphorus mass loading rate. The Bayesian approach was used for its simplicity in computation and its ability to accurately represent uncertainty. Applied to an Everglades wetland, the Bayesian method not only produced the probability distribution of the long-term phosphorus accretion rate but also generated a relationship of acceptable level of risk and optimal phosphorus mass loading rate for the proposed constructed wetlands in south Florida. The latter is a useful representation of uncertainty which is of interest to decision makers.¿ 1997 American Geophysical Union