erratum in cancer tissues 4 November 2013 Steve Horvath, Univ of California, Los Angeles As the author of the article, I have to report a correction. Fortunately, all of my results involving healthy, non-cancerous tissues are unaffected. But I have to report a correction for the cancer tissue data. In particular, I have to retract the statement that cancer is associated with an increased DNA methylation age (i.e. positive age acceleration) in most cancer types. While some cancer types show positive age acceleration, others exhibit negative age acceleration. I deeply regret this software coding error. Fortunately, all of the other statements about cancer remain largely intact since the coding error effectively added an offset term to predicted age. I am comforted by the fact that most of the reported results for cancer become even more significant and meaningful. A detailed description of the erratum can be found at my webpage: http://labs.genetics.ucla.edu/horvath/dnamage/correction We are currently in the process of posting a corrected version of the article. Meanwhile, please find updated Figures and Additional files for the cancer data application on the above mentioned webpage. Best regards, Steve Horvath Competing interests I have no competing interests. I am the author of the article.