Purpose Using data from American Society of Clinical Oncology ( ASCO) Annual Meetings, we determined the frequency, type, and monetary value of researchers' financial interests. Methods Financial disclosures for the 2004 ( 3,529 abstracts and 25,416 authors) and 2005 ( 3,556 abstracts and 26,181 authors) ASCO Annual Meetings were categorized into four groups: no author with a financial interest, research funding only, employment and leadership positions only, or at least one author with a personal financial interest. Interests were stratified by monetary value and other factors. Results In 2004 and 2005, 23% of abstracts had one or more authors with a personal financial interest. More than 75% of all personal financial interests were valued at less than $ 10,000. More than 90% of financial interests of more than $ 100,000 were employment related. Fewer than 3.5% of authors with personal financial interests had interests valued at more than $ 100,000. Overall, 6.3% ( 2004) and 2.9% ( 2005) of abstracts only had research funding, whereas 7.3% ( 2004) and 6.9% ( 2005) had only commercial employment. In 2005, 60% of plenary sessions compared with 23.1% in general poster sessions and 17.3% for publish-only abstracts reported financial ties. Personal financial interests were more common among US authors compared with non-US authors ( 9.2% v 4.2%). Conclusion About one fourth of abstracts at ASCO Annual Meetings have an author with a personal financial interest. Most personal financial interests are valued at less than $ 10,000 per year, whereas a majority valued at more than $ 100,000 are related to employees of commercial entities.