The authors respond to comments by P. G. Tuteur (see NIOSHTIC record NIOSH-00233773) on their article entitled, "Exposure Response Analysis of Mortality among Coal Miners in the United States," (American Journal of Industrial Medicine, Vol. 28, pages 167-184; see NIOSHTIC record NIOSH-00228462). The conclusion, that significant exposure/response relationships were found for cumulative exposure to respirable coal mine dust and mortality due to pneumoconiosis, or from chronic bronchitis or emphysema, was defended in this letter. With respect to Tuteur's suggestion that bias was introduced by misclassification of cases, that authors indicate that in order for such bias to explain the results of proportional hazard analysis, there would have had to have been consistent and systematic overdiagnosis of pneumoconiosis in relation to increasing cumulative exposure to respirable coal mine dust. Furthermore, despite the possible misclassification, the exposure/response relationship remained highly statistically significant for pneumoconiosis mortality and statistically significant for chronic bronchitis or emphysema mortality. These findings are supported by radiographic evidence of pneumoconiosis determined by independent readers. It was argued that the data analyses, which included both underlying and contributing causes of death, reduced the discrepancies concerning the primary cause of death. The authors claimed that workers aged 65 and older were excluded from analysis due to the healthy worker effect. Subsequent comparison of proportional hazards models with and without these workers showed that their exclusion had no effect on the results of the exposure/response analyses. The authors conclude that while their research is valid, further study of this cohort based on the available clinical information is crucial.