In an effort to align its college admission requirements with the new K-12 science standards, the University of California (UC) recently proposed to increase its high school science admissions eligibility requirement--known as area D--from two to three years. UC's new policy has the potential of improving student science learning and readiness for college, but could reduce eligibility and have negative effects on equity. This report examines how schools and students may fare under the new proposal. The University of California (UC) requires high school students to complete a series of college preparatory courses across a broad range of subjects, referred to as the A-G subjects, to be eligible for admission. During the 2017-18 school year, 19 percent of the A-G graduates in the sample completed only two years of science and may be affected by the new proposal. The number is higher among Latino (23%) and African American (23%) students, but a lot lower among white (12%) and Asian American students (10%). This report leverages data from a variety of sources to examine the potential impacts of the new proposal. First, it uses administrative records from the Transcript Evaluation Service (TES) and the A-G Course Management Portal (CMP) to identify the number and types of schools and students that may be affected by the proposal. Next, it looks at institutional factors that may encourage affected students to take another year of science through interviews with science teachers and school administrators. The report then uses administrative records from Cal-PASS Plus (CPP) to explore the benefits of a third year of science on postsecondary enrollment. Finally, it concludes by offering policy recommendations. [This report was written with research support from Courtney Lee. For the companion document containing technical appendices, see ED603921.]