Ectomycorrhizal (ECM) symbiosis improves markedly the P nutrition of the host plant, but the mechanisms sustaining this positive effect are not all understood. In our group, we focused on (1) the identification of fungal P transporters and (2) the role of fungal phosphatase (Pase) released into the soil solution on organic P (Po) mobilisation. To address the first question, we worked on the model fungal ECM species Hebeloma cylindrosporum. We identified two phosphate (Pi) transporters (HcPT1 and HcPT2) able to mediate Pi:H+ symport in yeast with different affinities for Pi. Expression patterns of the two genes in ECM plants grown in a low-P or high-P soil indicate that HcPT1 and HcPT2 might be involved in the uptake of Pi from the soil solution in the two conditions of soil P availability used. To address the second question, we worked on the quantification of Pase released by ECM tips collected in various forest ecosystems through Europe differing by their levels of water and nutrient availability. We used also H. cylindrosporum as this species is able to release huge amounts of Pase activity when grown in vitro in P-starved conditions. The results obtained so far showed that the regulation of Pase activity evaluated in situ is complex. H. cylindrosporum released four acid Pase fractions displaying different efficiency to release Pi from Po extracted from podzol. A novel scheme of the possible role of ECM fungal Pase in Po mobilisation from forest soil will be proposed.