['Underlying mechanism of mitotic checkpoint gene mitosis arrest deficiency 1 (MAD1) in human hepatocellular carcinoma (HCC) is rarely known.', 'We studied genetic change of the MAD1 gene as well as protein expression in 44 HCC and their associated non-cancerous surrounding liver tissues.', 'Genotype AG of MAD1 G-1849 A promoter was highly significant in microscopic vascular invasion than other genotypes (P = 0.006). Moreover, the mean tumor size of HCC with genotype AG (7.71 cm) was significantly larger than those of other genotypes (AA, 4.41 cm; GG, 4.59 cm; P = 0.033). After a median follow-up of 22 months, 18 (41%) of the 44 patients relapsed. Eleven (32.4%) of 34 with MAD1 protein expression and 7 (70%) of 10 with no expression of MAD1 protein showed tumor recurrence. The incidence of tumor recurrence in patients with the lost MAD1 expression was significantly higher than in those with the expressed MAD1 protein (P = 0.011).'] Is mitotic checkpoint gene MAD1 in hepatocellular carcinoma associated with tumor recurrence after surgical resection?