Cadmium inhibits DNA synthesis. The human fibroblast lines, F10-hTERT, F10-hTERT-LX1N, F10-hTERT-53-RNAi, F10-hTERT-p53-H179Q and GM02052A, were treated with cadmium during log-phase growth. During the 4 h treatment, DNA synthesis was measured every hour by incubation with [3H] thymidine for the final 30 min. After the 4 h treatment, the cadmium was removed, fresh medium added and DNA synthesis was measured at 1, 2, 6, 12 and 24 h later. Net [3H] radioactivity was normalized to cell number. Normalized [3H] CPM were graphed as a percent of time-matched, sham-treated controls. (#) denotes both F10-hTERT-p53-RNAi and F10-hTERT-p53-H179Q were significantly different than F10-hTERT and F10-hTERT- LX1N (p<0.05).