This report covers recent developments in resource adequacy (RA) assessments conducted to support long-range electric utility and system resource planning. It is based on a review of resource adequacy assessments related to planning studies from several recent resource plans across North America. The study finds that traditional RA methods related to planning reserve margins and capacity accreditation are still widely used in resource planning, though the methods used to evaluate RA and integrate results into planning are evolving. The paper is organized around six resource adequacy assessment factors: planning reserve margin, capacity accreditation, assessment of candidate portfolios, flexibility, uncertainty, and climate change and extreme weather. The report seeks to inform electric utility and system planners tasked with designing and implementing resource adequacy assessments and long-range resource plans within their organizations. For broader stakeholders, this report also provides information on the variety of resource adequacy analyses and methods applied across the industry.