Background: Proportionate representation of women in health research is an area for improvement. This study aims to assess the representation of women in gastrointestinal (GI) cancer clinical trials leading to FDA cancer drug approvals over the past 10 years. Methods: FDA cancer drug approvals between 07/2008-06/2018 were identified and trial reports supporting approvals sourced. The ratio of female to male (F:M) enrollment was compared with F:M cancer incidence in the U.S., and U.S. cancer prevalence and mortality. Results: Although F:M enrollment for all 229 trials leading to FDA cancer drug approvals in this period was similar to overall F:M cancer incidence in the U.S. (0.89 vs 0.86; Odds Ratio for female enrollment (OR) 1.05, 95% Confidence Interval (CI) 1.03-1.06, P<0.0001), in 17 trials that led to drug approvals in GI cancers there was lower F:M trial enrollment compared to cumulative U.S. incidence at those tumor sites (0.55 vs 0.79, OR 0.71, 95% CI 0.68-0.74, P<0.0001). F:M enrollment and U.S. incidence by the main GI tumor sites where approvals occurred is shown in Table. Female enrollment rates were also lower than U.S. female cancer mortality and prevalence rates in these tumor sites (P<0.0001 for all). Female enrollment in GI trials fell between 2008-2013 and 2014-2018 (38 vs 33%, OR 0.80, 95% CI 0.74-0.87, P<0.0001). Conclusions: Although disparity in female enrollment may be improving across combined FDA cancer drug approval trials, underrepresentation of females has persisted in GI cancer trials when compared to F:M cancer incidence, prevalence and mortality in the U.S. More work is required to determine the drivers of this disparity, in order to mitigate it.