This occasional paper presents national demographic subgroup data for the 1975-2019 Monitoring the Future (MTF) national survey results on 8th, 10th, and 12th graders' use of drugs, alcohol, and tobacco. The 2018 subgroup data presented in this report accompany the "Monitoring the Future National Survey Results on Drug Use: 1975-2019: Overview, Key Findings on Adolescent Drug Use" (see ED604018) and the "Monitoring the Future National Survey Results on Drug Use, 1975-2018: Volume I, Secondary School Students" (see ED599067). The trends presented in this occasional paper in tabular and graphic forms cover demographic subgroups based on: (1) Gender; (2) College plans; (3) Region of the country; (4) Population density; (5) Education level of the parents (a proxy for socioeconomic level); and (6) Racial/ethnic identification. Detailed descriptions of the demographic categories are provided. The graphs and tables in this occasional paper present trend data for 8th-, 10th-, and 12th-grade respondents separately. Data for 12th grade begins with 1975, the first year in which a nationally representative sample of high school seniors was surveyed. Data for 8th and 10th grades begin with 1991, when the study's nationally representative annual surveys were expanded to include those lower grade levels.