We have investigated the effects of ZrC and ZrB 2 doping on the superconducting properties of the powder-in-tube processed MgB 2 /Fe tapes. Samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), transport and magnetic measurements. We confirmed the following quite different roles of ZrC and ZrB 2 in MgB 2 . ZrC doping was found to decrease the transport critical current density (J c ) at 4.2 K, while the critical temperature (T c ) kept constant. In contrast, the J c values in magnetic fields were enhanced greatly by the ZrB 2 addition, which resulted in a decrease in T c by only 0.5 K. The reason for different effects of two dopants is also discussed.Extensive research efforts have been made to improve the performance of MgB 2 materials since the discovery of superconductivity at 39 K in this compound [1] . However, a rapid decrease in critical current density (J c ) at magnetic fields in MgB 2 is the principal limitation to their technological applications. This limitation is strongly correlated to poor grain connection and lack of pinning centers. Hence, chemical doping using different elements/compounds seems to be the best and most practical route [2][3][4][5][6] . Of all the chemical dopings undertaken, Zr and C doping have been successful in enhancing both the irreversibility field (Hirr) and J c (B). The remarkable improvement of J c (B) behavior in the above-doped samples can be explained by the densification effect and the improved pinning [2,4] . The intention of the present work is to study the effect of ZrC and ZrB 2 additions on the phase formation and microstructures of MgB 2 as well as their roles in the J c enhancement. It should be noted that the transitionmetals ZrC and ZrB 2 are potential ceramic materials highly resistant to high temperatures, wear, oxidation and corrosion. They have a very good thermal and electrical conductivity [7] . In this study, we show how ZrC and ZrB 2 affect the properties of MgB 2 tapes made by powder-in-tube technique. We have found quite different behaviors between ZrC and ZrB 2 in MgB 2 .