mendelFix is a Perl script for checking Mendelian errors in genome-wide SNP data of trio designs. The program takes 12-recoded PLINK PED and MAP files as input, and calculates a series of summary statistics for Mendelian errors, sets to missing offspring genotypes that present Mendelian inconsistencies, and implements a simplistic procedure to infer missing genotypes using parent information. The program can be easily incorporated in any pipeline for family-based SNP data analysis, and is distributed as free software under the GNU General Public License.