General Utilities for Genotyping Study (GUGS) is a toolbox for aiding the analysis of DNA marker data and its design in Microsoft Excel (MS Excel). GUGS provides more than 100 flexible functions for the manipulation, evaluation, and conversion of genotype data. It also provides functionalities for genotype format conversion to support linkage analysis using JoinMap software, frequency analysis for population genetics, parentage analysis, and statistical genetic analysis. Its functionality for the manipulation of nucleotide or amino acid sequences also assists DNA marker design. These GUGS features enable users to conduct all steps from DNA marker design to preliminary evaluation, data analysis, and format conversion for advanced study in a single environment without having to export/ import data. GUGS is freely available at https://github.com/tokurou/GUGS under the GPL v3 license.