We report the results of isochronal annealing study of deep levels in Rh-doped n-type GaAs grown by metal-organic vapor phase epitaxy (MOVPE). Deep level transient spectroscopy (DLTS) technique has been employed to study the effects of annealing on deep levels in Rh-doped p + nn + junction samples. A majority-carrier emitting band of deep levels along with a high temperature peak (RhE1), corresponding to deep level energy position E c ร0.92 eV and a minority-carrier emitting band of deep levels are identified with Rh-impurity prior to thermal annealing of our samples. In addition to these Rh-related deep levels, the well-known native defect EL2 at E c ร0.79 eV is observed in majority-carrier emission spectra and two inadvertent deep-level defects, H1 at E v +0.09 eV and H3 at E v +0.93 eV, usually observed in reference (without Rh) samples, are also detected in the minority-carrier emission spectra of Rhdoped samples. At least one level is found to be introduced at E c ร0.13 eV in Rh-doped samples at about the same temperature position as the level E(A)1, observed in reference samples, as a result of isochronal annealing, while the other two levels observed in reference samples could not be seen in annealed Rh-doped samples. Data on the annealing behavior and other characteristics of both Rhrelated bands of deep levels observed in majority-and minority-carrier emission DLTS spectra, as well as for the high temperature Rh-related electron-emission peak, are presented. Possible interpretations of these results for the nature and structure of the different deep-level defects are discussed.