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The progression of a normal cell to senescence in vivo and in vitro is accompanied by a reduction in the length of the telomeres, the chromosome capping segments at the end of each linkage group. However, overexpression of the reverse transcriptase subunit (HTERT) of the ribonucleoprotein telomerase restores telomere length and delays cellular senescence. Although some data exist in the literature with respect to survival, no molecular data have shown that DNA repair in telomerase-immortalized cells is normal. Several telomerase-immortalized human skin fibroblast cell lines were constructed from a primary human fibroblast cell line. The primary line and the telomerase-immortalized cell lines were treated with either ultraviolet (UV) radiation or dimethylsulfate (DMS). UV radiation principally produces cyclobutane pyrimidine dimers that are repaired by nucleotide excision repair, whereas DMS introduces mainly N-methylpurines repaired by base excision repair. Here, we show that repair of both types of damage in the telomerase-immortalized human skin fibroblast cell lines is identical to repair observed in normal skin fibroblasts. Thus, telomerase expression and consequent immortalization of skin fibroblasts do not alter nucleotide or base excision repair in human cells.