The feasibility is investigated of performing nonlinear least-squares fits of Mossbauer spectra within a microprocessor-based Mossbauer spectrometer. The development of a ROM-based Pascal program for a spectrometer using a Motorola 6800 microprocessor is described. The time taken to fit a 256-channel spectrum to one Lorentzianshaped line is about 100s per iteration. The fitting program is most useful in fitting relatively simple Mossbauer spectra, such as those obtained in most analytical applications, in teaching applications, or where the user does not have easy access to a mainframe computer