The purpose of this study was to determine the incidence of the loss of heterozygosity (LOH) among normal cervixes, cervical intraepithelial neoplasias (CINs) and invasive cervical cancers (ICCs). DNA samples (136) were obtained from 31 normal cervixes, 49 CINs and 56 ICCs. Four polymorphic microsatellite markers (D3S1300, D3S1351, D3S1478 and D3S4103) covering the chromosome 3p arm, were employed. LOH at one or more loci were identified in: 9/31 (8.1%) normal cervixes, 17/49 (14.6%) CINs and 26/56 (22.1%) invasive cancers. The incidence of the LOH at 3p varied for each locus and ranged from 5.6% for D3S1351 to the highest rate of 16.6% for D3S1300. We thus found that LOH of chromosome 3p can occur in normal cervixes and that incidences increase in CINs and ICCs. Deletion in the 3p14.2 (D3S1300) and 3p21.2 (D3S1478) regions might be an early event and, in fact, necessary for cervical cancer progression. The loss of function of tumor suppressor genes (TSGs) located in these regions may have a sequential effect in cervical cancer carcinogenesis.