Monitoring the Future (MTF) is a long-term study of substance use and related factors among U.S. adolescents, college students, and adult high school graduates through age 60. It is conducted annually and supported by the National Institute on Drug Abuse. MTF findings identify emerging substance use problems, track substance use trends, and inform national policy and intervention strategies. MTF is designed to detect age, period, and cohort effects in substance use and related attitudes. Age effects are similar changes with age seen across multiple class cohorts; they are common during adolescence. Period effects are changes that are parallel over a number of years across multiple age groups (in this case, all three grades under study--8, 10, and 12). Cohort effects are consistent differences among birth cohorts (or in this case, class cohorts) that are then maintained as the cohorts age. The key findings regarding use of various substances by 8th, 10th, and 12th graders surveyed across the coterminous U.S. in 2018 are presented in this report. [For "Monitoring the Future National Survey Results on Drug Use, 1975-2017: Overview, Key Findings on Adolescent Drug Use," see ED589762.]