An error crept into this editorial by Gavin Yamey and Peter Hotez during the editing process and persisted to publication (BMJ 2007;335:269-70, 11 Aug, doi: 10.1136/bmj.39281.645035.80). The cost of the four drugs for controlling seven major tropical diseases for 500 million people in Africa should have been about $0.50 (£0.25; €0.36) per person each year—much lower than the $50 stated in the article.