To determine phosphorus (P) losses from agricultural land to surface water, information is needed about the behavior of P in soils. In this study, the sorption and desorption characteristics of lowland peaty clay soils are described based on experimental laboratory studies. The maximum P sorption capacity is comparable to that of acid sandy soils if based on the amount of oxalate-extractable aluminum and iron. A fraction of the maximum amount of sorbed P is bound reversibly (Q), which can be measured with an iron-impregnated paper. The fraction of the maximum reversibly sorbed P depends on the amount of oxalate-extractable aluminum and iron. In the topsoil, the maximum of the fraction of reversibly bound P (Qm) is about one third of maximum P sorption capacity; and in the subsoil, about two thirds. All sorption and desorption parameters are related to soil characteristics of peat samples.