IMPORTANCE Gender disparity exists among authors of the oncology literature. OBJECTIVE To quantify trends in authorship by gender within a comprehensive data set of Medlineindexed oncology articles in medical journals with high impact factors. DESIGN, SETTING, AND PARTICIPANTS This cross-sectional study used Medline citations to examine archives of research journals from 3 disciplines in the oncology literature. Authors from all oncology-related articles with Medical Subject Headings terms assigned from 2002 to 2018 from 13 general oncology/medicine, radiation oncology, and surgical journals were included for analysis, encompassing clinical trials, observational studies (excluding case reports), reviews, systematic reviews, meta-analyses, and all other published articles. Data were analyzed between April and May 2020. EXPOSURES Authors were assigned genders based on societal naming norms via third-party gender identification service Gender-API.com. This assignment was internally validated based on manually obtained publicly available data on the internet. MAIN OUTCOMES AND MEASURES Trend in female authorship over time while considering journal type, authorship position, and article type.RESULTS A total of 420 526 authors from 58 368 articles were found, of which 400 945 were assigned a gender based on their name. In total, 29.5% (95% CI, 29.4%-29.6%) of authors were identified as female, rising from 25.5% (95% CI, 24.7%-26.3%) in 2002 to 31.7% (95% CI, 31.2%-32.3%) in 2018. Each subgroup of primary article type by journal type saw a rise in female authorship over the studied period.