The steelworker cohort had been assembled from personnel records at three steel plants. Names and Social Security numbers were known for each cohort member. NIOSH, as a federal agency, had access to Internal Revenue Service tax data regarding current addresses of Those paying taxes, and these were used to locate live cohort members. Addresses from the death certificate were used to locate next of kin for the decedents. Directory assistance was used to obtain telephone numbers when addresses were not helpful.