The analysis of the literature demonstrated that pharmacy counselling influenced patient outcome after transplantation. This was the reason we established pharmacy consultation in 1999. The aim of this study was to determine patient knowledge before and after pharmacy counselling. Twenty-nine patients were questioned about the identification, role and dosage of prescribed drugs. The mean duration of pharmacy counselling was 54 minutes. Before pharmacy consultation, the knowledge score was 53.7%. Afterwards, the mean score value reached 75% and seven patients had a score of 100%. The anti-rejection therapy was understood by 93% of patients. However, the associated drugs were poorly known: less than 15% of patients initially knew about the purpose of the antimicrobial agent, compared with 50-60% after counselling. During counselling, two women were identified as regularly using St John's Wort and were informed that this herbal medicine can endanger the success of organ transplantation. Five patients or family members called the pharmacist to obtain additional information. Among these, two medication errors, both with corticosteroid drugs, were reported by family members of patients of foreign origin who had difficulty in understanding and speaking French. Pharmacy counselling improved patient knowledge about therapy after transplantation.