Irrigation reuse of municipal effluents conserves freshwater resources and avoids direct nutrient discharges to surface waters. The sustainability of agricultural reuse programs, however, may be challenged by evolving phosphorus (P)-based nutrient management policies. This paper assesses the agricultural and environmental implications of soil P accumulation from effluent irrigation and discusses sustainability under guidelines to control P export in agricultural runoff and drainage. For typical regulatory maximum irrigation rates (5.1-cm-wk-1), secondary effluents containing 3-4-mg-P-L-1 provide ∼90-kg-P-ha-1-yr-1 and cause soil P enrichment beyond levels needed for optimum crop yields. Applied P potentially falls short of crop needs for advanced wastewater treatment processes with low (<0.5-mg-L-1) effluent P or where hydraulic rates are restricted by soil, climatic, or regulatory conditions. Except for some locations where well-drained low P-retention soils overlie shallow groundwater, effluent-irrigated P has minimal impact on water quality. Most site assessment tools (P indices) were developed to identify fields with high P loss vulnerability from manure and commercial fertilizer application and do not explicitly address effluent-applied P. Adoption of P-management regulations not accounting for the differential behavior of P in effluent-irrigated fields may unnecessarily restrict agricultural irrigation of reclaimed water. © 2012 American Society of Civil Engineers.