Purpose: Updated estimates of adolescents' receipt of sex education are needed to monitor changing access to information. Methods: Using nationally representative data from the 2006-2010 and 2011-2013 National Survey of Family Growth, we estimated changes over time in adolescents' receipt of sex education from formal sources and from parents and differentials in these trends by adolescents' gender, race/ethnicity, age, and place of residence. Results: Between 2006-2010 and 2011-2013, there were significant declines in adolescent females' receipt of formal instruction about birth control (70% to 60%), saying no to sex (89% to 82%), sexually transmitted disease (94% to 90%), and HIV/ AIDS (89% to 86%). There was a significant decline in males' receipt of instruction about birth control (61% to 55%). Declines were concentrated among adolescents living in nonmetropolitan areas. The proportion of adolescents talking with their parents about sex education topics did not change significantly. Twenty-one percent of females and 35% of males did not receive instruction about methods of birth control from either formal sources or a parent. Conclusions: Declines in receipt of formal sex education and low rates of parental communication may leave adolescents without instruction, particularly in nonmetropolitan areas. More effort is needed to understand this decline and to explore adolescents' potential other sources of reproductive health information. (C) 2016 The Society for Adolescent Health and Medicine. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).