Thank you for your response. I have been using start values for peak location and line width, prior knowledge as recommended by the jMRUI help menu and putting in soft constraints on the location of the peak. However, there are times when jMRUI still does not find the peak I am looking for, despite clearly seeing the peak within the spectra. Often this occurs with PME and resting Pi peaks. Is there a way to manually fit those peaks or otherwise quantify them when they are not recognized by jMRUI?