This project is part of a multi-year program to gather detailed information about substance-use patterns among Texans. Investigators interviewed a total of 946 youths, age 10 to 17, as they entered Texas Youth Commission (TYC) reception facilities. Results show that 81% of TYC youth have used illicit substances--51% in their last month on the street. Substance use was pronounced even among those aged 13 and younger. Some 91% of TYC youth have tried alcohol, 86% have used tobacco, and 39% sampled inhalants. Age had little effect on patterns of current use although children 13 years and younger were more likely than those age 16 and 17 to report current use of inhalants. Whites and Hispanics recorded much higher lifetime and current prevalence of substance use than did Blacks. While clear and consistent racial/ethnic differences in reporting on drug use became obvious, these were only differences of degree. Many TYC youth reported daily substance use and TYC youth were more likely than individuals in school to be current users of most substances. Those aged 13 or younger appear to be particularly at risk for developing severe problems. This report contains 17 figures which explicate youth behavior and substance use. Ten appendices summarize the data accumulated for the study. (RJM)