The availability of P for pasture plants in a range of acid hill soils with organic matter content up to 80 % was assessed by extraction, exchange, sorption, isotopic dilution and digestion methods and was verified by plant P uptake using ryegrass and white clover as test plants. Values obtained by the conventional extraction and equilibration methods were inversely but non-significantly related to P uptake expressed in mg kg-1 units: the relationships were only marginally improved with the data in mg litre-' units. The size of labile pool ('I,' value) and amounts of both total-and organic-P ranked the soils in the same order as P uptake, but only when the data were expressed in mg litre-1 units were the relationships highly significant. Reasons are suggested for the unsuitability of conventional extraction methods for acid, organic hill soils. Organic-P (in mg litre-' units) may provide the best indication of soil P status, but the determination of total-P appears to be the most practical alternative.