This occasional paper presents subgroup findings from the Monitoring the Future (MTF) study on levels of, and trends in, the use of a number of substances for nationally representative samples of high school graduates ages 19-30, "Monitoring the Future National Survey Results on Drug Use, 1975-2018. Volume II, College Students & Adults Ages 19-60" (see ED599071). The data have been gathered in a series of follow-up surveys of representative subsamples of high school seniors who were first surveyed in 12th grade as part of the MTF study. Therefore, the universe being described omits people who did not complete high school--between 8 and 15% of each age group, with the most recent class cohorts closer to the bottom of that range. Surveys of the graduating cohorts of high school seniors started in 1976 and have continued with each graduating class since. Data were first available for the 19-22 age group in 1980 and for the older age groups in subsequent years, as the tables and figures in this occasional paper indicate. The general epidemiological findings from these samples are discussed in "Volume II" of the annual monograph series. The subgroup trends shown in this occasional paper complement the last section of Chapter 5 (Trends in Drug Use in Early and Middle Adulthood) of that monograph by presenting the trend data for young adult subgroups in both graphic and tabular form. The results are described and discussed in Chapter 5, but the extensive set of tables and figures is provided in this paper for the reader who wishes to view the figures and the underlying numerical values. Three demographic dimensions are differentiated: gender, region of the country, and population density. Gender includes trends for males and females; region describes trends for each of the four major regions defined by the U.S. Census; and population density differentiates trends for five levels of community size. The Table of Contents and List of Figures in this occasional paper contain links to the content and figures. Following each figure is a table giving the numerical values associated with each trend line in that figure.