A radioisotope-identification and mass-determination subroutine has been added to the gamma-ray spectrum analysis program SAMPO. The subroutine IDENT contains a nuclear data library of 750 gamma-rays that are likely to be encountered in thermal-neutron activation analysis. Peaks found by SAMPO are compared with the library peaks and possible isotope identifications are made. To maximize the degree of confidence in the isotope identification, the subroutine carries out a half-life check and also confirms that the most prominent gamma-ray of the isotope concerned is present. Using the library data, together with information on the neutron flux, duration of the irradiation, subsequent decay time, and gamma-detection efficiency, the subroutine calculates the masses of elements identified in the sample, and can handle spectra acquired during either simple or cyclic irradiation. As well as the calculated masses the output contains information on identifications rejected by certain criteria. The nuclear data library used by the subroutine is presented in this paper in a simplified tabular form, and, as such, may be used for direct isotope identification and elemental mass determination.