The article deals with the contribution of tacrolimus (Prograf) to improvement in kidney transplant results. Tacrolimus, in comparison with cyclosporine significantly reduces the incidence of acute rejection and improves survival of grafts as well as patients. Based on the literature, the primary immunological differences between tacrolimus and cyclosporine effects are pointed out. These differences explain the better immunosuppressive effectiveness of tacrolimus. Based on analysis of the results, subclinical rejection problems and significance of protocol biopsy for present-day transplantology are discussed. There is also a critical analysis of the questions, which priority, in relationship to the expanding availability of immunosuppressive substances currently has high interest for nephrologists researching subclinical rejection.