Non-adherence to immunosuppressive therapy in patients following solid organ transplantation is associated with an increased risk of transplant rejection and graft loss. A high pill burden can adversely affect patients' implementation of their treatment regimens and may lead to omitting doses of medication. The aim of this study was to investigate medication implementation adherence in liver and kidney transplant recipients converted from twice-daily, immediate-release tacrolimus to once-daily, prolonged-release tacrolimus.