About two-thirds of heads of department from 140 medical schools and teaching hospitals in the US have some relationship with the pharmaceutical industry.
Five of the 459 heads admitted to receiving gifts such as tickets to sporting events in the last year, something industry guidelines generally prohibit.
Department heads said they were happy to accept grants of less than 10,000 dollars for educational purposes, but showed concern about larger payments.
Campbell said that financial incentives could make them less vigilant about ensuring that educational materials and research plans were not biased towards specific treatments, reports the New Scientist.
The study has been published in The Journal of the American Medical Association.