Loss of Heterozygosity (LOH) on chromosome 9p21 (D9S319) from fifty-four laryngeal cancer patients has been examined by using the PCR technique of DNA microsatellite markers in this study. The results showed that the LOH on 9p21 was 100% present (2/2) in in situ carcinomas and 66% (29/44) in invasive carcinomas. Therefore, these results suggest that there is a tumor suppressor gene located on 9p21 region. Its inactivation was related to laryngeal carcinoma and it was an early event.