Gadolinium (Gd) isotopes are widely encountered in criticality safety and reactor applications. They are listed in the APPENDIX B of the US Department of Energy, Nuclear Criticality Safety Program (NCSP). The Institut de Radioprotection et de Sûreté Nucléaire (IRSN) works close to NCSP to address data issues pertinent to criticality safety. New evaluation of Gd isotopes, 152Gd, 154Gd, 155Gd, 156Gd, 157Gd, 158Gd, and 160Gd, in the resolved resonance region has been performed with the code SAMMY. The resonance evaluations of these isotopes are in response to issues in connection to critical benchmark results and reactor physics analysis of power reactors. Furthermore, one of the main objectives is to understand and to generate more accurate cross sections and to improve their uncertainties and correlations thru the cross-section covariance representation. Both the resonance parameter and resonance parameter covariance are derived by a combination of the codes SAMMY, SAMDIST, and SAMINT. SAMMY is basically a differential evaluation tool based on the R-matrix theory for the cross section; SAMDIST verifies the statistical properties of resonance parameters while SAMINT permits the incorporation of integral data in the evaluation process. The differential data used in the evaluation are transmission and capture cross section data available in the EXFOR database whereas critical benchmarks were those accessible in the ICSBEP database.