Editor–Owing to the charged atmosphere surrounding the issue of passive smoking, our paper provoked strong reactions on bmj.com. The most disturbing reactions have come from the enforcers of political correctness who pose as disinterested scientists but are willing to use base means to trash a study whose results they dislike. They have no qualms about engaging in personal attacks and unfounded insinuations of dishonesty rather than judging research on its merits.1 The resulting confusion has misled many readers and diverted attention from the facts of the study.

Since 15 May Michael Thun of the American Cancer Society has led a campaign to discredit our study, including his letter above. However, almost every sentence in his letter is misleading, and he disregards key information in the full version of our paper. Contrary to the title of his letter, we have presented an accurate analysis of the California cohort of the cancer prevention study I (CPS I), not disinformation, and it comes from the University of California, Los Angeles, and the State University of New York, Stony Brook, not the tobacco industry.

Anyone who reads the full version of the paper and our response to the reviewers of 9 January2 will see that in fact we provided detailed evidence that refutes the claim that our study is “fatally flawed because of misclassification of exposure.” Contrary to Thun's …