The deficiencies of nucleotide excision repair (NER) factors are genetic diseases, xeroderma pigmentosum (XP) increasing risk of developing cancer on sun-exposed areas of the skin. However, the abnormality of NER factors in human sporadic carcinoma remains unclear. Loss of heterozygosity (LOH) analysis for the XP, XPA, XPB, XPC, XPD, XPE, XPF, XPG and the transcription-coupled repair factor, Cockayne syndrome B (CSB) revealed that NER factors were abnormal in 62.1 % of ovarian tumors (18/29), 16.7% of colon (2/12) and 22.2% lung (2/9) carcinomas. Furthermore, 13.8% of ovarian, 8.3% of colon and 22% of lung carcinomas exhibited LOH for NER factors without LOH for tumor suppressor genes such as p53, FHIT, APC, BRCAI, BRCA2 and DCC. Although both microsatellite instability and LOH of NER factors were observed in some cases, there was no strong association between them in the present study. These observations raise the possibility that alterations of NER factors may be frequent in human sporadic carcinomas. Further study should be needed to find the direct evidence of NER gene abnormalities in human sporadic carcinoma tissues.