Background Posaconazole (PCZ), an orally-administered extended spectrum antifungal agent, is used in the prophylaxis and salvage treatment of invasive fungal infections (IFIs) in patients receiving chemotherapy or haematopoietic stem cell transplantation. In curative treatments, maintenance of trough plasma concentrations between 0.5 and 1.5 mg/L seems to be associated with clinical efficacy. In prophylactic use, a threshold of 0.5 mg/L corresponds to a minimum exposure. In order to maximise PCZ exposure, the Pitié-Salpêtrière hospital’s haematology department has set up extensive strategies for training the medical team, including on the concepts of drug interaction with food, beverages or other drugs and optimising the frequency of drug administration. Purpose To investigate the impact of this advanced medical training on posaconazole plasma concentrations on the effectiveness of treatment. Materials and methods Patients were treated with PCZ for IFIs in the haematology department. Plasma concentrations were measured by a validated high performance liquid assay (HPLC) with UV detection. For each patient, criteria such as age, sex, dose and PCZ plasma concentrations were collected between January and September 2013. Medical training was performed in June 2013. Results In this retrospective study, 33 patients were included; 26 men and 7 women, the average age was 50.3 ± 13.9 years. 62 serum posaconazole concentrations were recorded. The dose of PCZ administered was 806 ± 323 mg/d. In the second group (after medical training), PCZ plasma concentrations were significantly higher than in the first one (1.08 ± 0.70 mg/L vs. 0.72 ± 0.45 mg/L, p = 0.036). In addition, the doses of PCZ administered were also significantly lower in the second group (686 ± 255 mg vs. 915 ± 343 mg, p = 0.004). Conclusions This study shows the importance of medical staff training on posaconazole bioavailability and confirms the usefulness of monitoring posaconazole in oral suspension. No conflict of interest.