 We will derive descriptive statistics prevalence of malignancy, sensitivity, specificity, and false negative rates. The overall sample size will be 500 patients who had PTNB of a lung mass within the study period. Approximately 80 are expected to have a biopsy result showing no evidence of malignancy, based on a retrospective review performed under an IRB exemption 87-04, letter dated 92804. The expected proportion of cases with no evidence of malignancy is approximately 0.15. For a 95 confidence interval of 0.15-0.075 we will need follow-up information from 61 patients, considering that this is a descriptive study with a dichotomous variable. This gives us a margin for patients who will be lost to follow-up 