<i>GEN1</i> mRNA and protein expression were reduced in primary endometrial cells from endometriosis patients compared with controls (mRNA: 0.52 ± 0.14 vs. 1.00 ± 0.19, <i>p</i> = 0.05; immunofluorescence intensity: 0.54 ± 0.18 vs. 1.00 ± 0.22, <i>p</i> = 0.05). The gene discussed is GEN1; the disease is endometriosis.