In this study, we investigated the haplotypes of six GJB2 mutations frequently observed in Japanese hearing loss patients (i.e., c.235delC, p.V37I, p.[G45E; Y136X], p.R143W, c.176_191del, and c.299_300delAT) and analyzed whether the recurring mechanisms for each mutation are due to founder effects or mutational hot spots. The gene discussed is GJB2; the disease is hearing loss disorder.