As part of its ongoing health surveillance program, Koppers sponsored three analyses of data collected as a result of an historical prospective study of eight of its coal tar facilities. The cohort for the study.consisted of 4,048 individuals who were employed for at least ten consecutive days between January 1, 1946 and December 31, 1977 in other-than a strictly secretarial or clerical capacity at any one of the facilities. After the study was concluded and the data analyzed, it is obvious that all three analyses are inconclusive because the data collected in the study did not include the smoking habits of all employees.