Muscular dystrophies (MD) comprise a heterogeneous group of hereditary myopathic diseases. In this group, myotonic MD is associated with an increased cancer risk. However, the cancer risk in other types of MD is unclear. To address this gap in knowledge, we assessed data obtained from the Taiwan Health Insurance Program database. A total of 1,272 patients with MD diagnosed between 1997 and 2009 were enrol ed. They were fol owed up for cancer during the same period by record linkage with the cancer certification in Taiwan. Age- and sex-standardized incidence ratios (SIRs) of overall and site-specific cancers were calculated. For congenital and progressive hereditary MD, there were 685 and 505 cases (males:69.5%and 80.6%), the median ages at diagnosis were 16 and 13 years, and the mean fol ow-up durations were 7.12 and 5.06 years, respectively. In addition, cancers were developed in 10 patients with congenital MD and 3 patients with progressive hereditary MD. Female MD patients exhibited an increased cancer risk, yielding an SIR of 3.37 [95%confidence interval (CI)=1.38-8.25] in congenital MD and 2.95 (95% CI = 0.95-9.19) in hereditary progressive MD. Site-specific cancer SIRs were not powered to be significantly different. In conclusion, genetic defects in hereditary MD may increase cancer risks in females and a sex difference should be further investigated.