This study analyzed oncology clinical trials to identify sex differences in outcomes and toxicity. It found that only 0.5% of 89,221 oncology trials included curated post-treatment sex comparisons. Among 288 trials with survival, outcome, or response comparisons, 16% reported better survival or response in males, while 42% reported better outcomes in females. The strongest differences were observed in trials of EGFR inhibitors in lung cancer and rituximab in non-Hodgkin's lymphoma, both favoring females. Among 44 trials with side effect comparisons, more trials reported fewer side effects in males than in females. Despite the legal requirement to compare males and females, such comparisons are rarely reported. The study highlights the need for more thorough reporting of sex differences in future trials. The U.S. Public Health Service Act and NIH policies require sex comparisons in clinical trials. Since 2016, NIH has mandated analysis of sex as a biological variable in preclinical studies. However, these policies are not widely followed, and there is a lack of understanding that the requirement is to compare by biological sex, not by self-identified gender. The study found that only 26 out of 107 NIH-funded trials reported at least one outcome by sex or included sex as a covariate in statistical analysis. Subgroup analyses of males and females separately do not constitute a comparison. Designing, analyzing, and evaluating clinical trials to examine and compare treatments in both sexes requires careful planning. It is important to recruit sufficiently many males and females to have some power to detect differences. Regulators must be clear and consistent about what sex-specific subgroup analyses and sex comparison analyses are expected in filings reporting trial results. Differences in proper doses between males and females should be planned and should also consider the patient's age and pharmacogenomic markers. Previous findings about differences in sex by survival, response and other outcomes are varied. For example, there has been much debate about whether males have better outcomes in response to immunotherapy. Others have hypothesized that females may have better survival in oncology clinical trials given their better survival in real-world data. A very recent meta-analysis of oncology trials leading to drug approvals in the USA found no general significant differences in outcomes between males and females, even though individual trials may have significant differences. In contrast, most studies and reviews on differences in side effects and toxicities by sex claim that females in oncology clinical trials experience more drug toxicities and other adverse events than males. However, one recent large study reached the opposite conclusion. Given the complex and unclear state of sex disparities in clinical cancer research, the purpose of this study is to comprehensively characterize sex outcome comparisons in all oncology interventional clinical trials and to identify those comparisons that find a significant difference between males and females. The study found that females demonstrate better survival outcomes and treatment responses in the majority of clinical trials that doThis study analyzed oncology clinical trials to identify sex differences in outcomes and toxicity. It found that only 0.5% of 89,221 oncology trials included curated post-treatment sex comparisons. Among 288 trials with survival, outcome, or response comparisons, 16% reported better survival or response in males, while 42% reported better outcomes in females. The strongest differences were observed in trials of EGFR inhibitors in lung cancer and rituximab in non-Hodgkin's lymphoma, both favoring females. Among 44 trials with side effect comparisons, more trials reported fewer side effects in males than in females. Despite the legal requirement to compare males and females, such comparisons are rarely reported. The study highlights the need for more thorough reporting of sex differences in future trials. The U.S. Public Health Service Act and NIH policies require sex comparisons in clinical trials. Since 2016, NIH has mandated analysis of sex as a biological variable in preclinical studies. However, these policies are not widely followed, and there is a lack of understanding that the requirement is to compare by biological sex, not by self-identified gender. The study found that only 26 out of 107 NIH-funded trials reported at least one outcome by sex or included sex as a covariate in statistical analysis. Subgroup analyses of males and females separately do not constitute a comparison. Designing, analyzing, and evaluating clinical trials to examine and compare treatments in both sexes requires careful planning. It is important to recruit sufficiently many males and females to have some power to detect differences. Regulators must be clear and consistent about what sex-specific subgroup analyses and sex comparison analyses are expected in filings reporting trial results. Differences in proper doses between males and females should be planned and should also consider the patient's age and pharmacogenomic markers. Previous findings about differences in sex by survival, response and other outcomes are varied. For example, there has been much debate about whether males have better outcomes in response to immunotherapy. Others have hypothesized that females may have better survival in oncology clinical trials given their better survival in real-world data. A very recent meta-analysis of oncology trials leading to drug approvals in the USA found no general significant differences in outcomes between males and females, even though individual trials may have significant differences. In contrast, most studies and reviews on differences in side effects and toxicities by sex claim that females in oncology clinical trials experience more drug toxicities and other adverse events than males. However, one recent large study reached the opposite conclusion. Given the complex and unclear state of sex disparities in clinical cancer research, the purpose of this study is to comprehensively characterize sex outcome comparisons in all oncology interventional clinical trials and to identify those comparisons that find a significant difference between males and females. The study found that females demonstrate better survival outcomes and treatment responses in the majority of clinical trials that do