The inactivation of p53 and rb genes has been implicated in the pathogenesis of cervix uteri carcinoma. Although this neoplasia presents high incidence and mortality rates in Chile, there are not studies about its molecular abnormalities. We investigated the frequency of loss of heterozygocity (LOH) at p53 and rb genes in 17 invasive squamous cell carcinomas of the cervix uteri, using microdissection technique from microslides and microsatellite sequences amplification by PCR. Moreover, we investigated the immunohistochemical expression of p53 protein in 30 invasive squamous cell carcinomas LOH was detected in 6/12 of informative cases (50%) at p53 gene and in 3/10 (30%) at rb gene. The p53 protein immunohistochemical expression was 47% (14/30 cases). LOH at p53 gene in cases without p53 protein immunohistochemical expression was observed. We concluded that p53 gene molecular abnormalities are important in the pathogenesis of squamous cell carcinoma of the cervix uteri, in contrast than LOH at rb gene.