The magnitude a/substance abuse and HIVIAIDS pandemics is ever increasing alld has broughtrnmultidimensional challenges. among youths in particular, and entire nations in general.rnHowever, dala regarding the contribution of substance abuse to the spread of HIVIAIDS isrnscanty in Ethiopia.rnThis study was conducted 10 explore youth substance abuse and HIVIAIDS in Adamo Town. Tornthis end, the following research questions were raised: I) What is lite magnitude of substance abusernamong youth? 2) What jactors trigger young people 10 resort 10 substance abuse? 3) What is tlte effect ofrnsubstance abuse, especially its contributio" /0 the spread of HIVIAfDS? The study was based on 81rndays a/fieldwork using questionnaire surveys, in-depth interviews, observation, 6 Focus GrouprnDiscussions and 5 case histories.rnThe findings showed that different types of substances (chat, alcohol, shisha, tobacco, cannabisrnand inhalants) are abused either separately or in combination, 10 a great extent among youthsrn(15-29 years old). Particularly, Catha edulis (chat) plays initiating role in cal/sing youths 10rnfurther ,ake other substances. The substances are either locally available or imported.rnThe youth are indulged in substance abuse for different reasons. Merton's anomie theory;rnLindesmith's theory of addiction; and sub cultural pallerns and drug abuse model are thereforernemployed 10 comprehend the factors that (rigger the youth to substance abuse and thernsubsequent ramifications. Accordingly the study identified major reasons for abusing substancesrnsuch as peer influence, psychological, and socioeconomic factors.rnMost abusers began consuming habit-forming substances at early ages when they were unable torndifferentiate between good and bad. Some substance abusing practices have ceremonies andrnprocesses that sometimes pave the way for sexual intercourse. Most often youth substancernabusers indulge in unsafe sexual intercourse after they abuse substances.rnPsychological and social problems, economic crisis, and health problems are some of the effectsrnthat stem from substance abuse. Moreover, abusing substances could aggral'ate the spread ofrnHIVIAIDS. The efforts made by some organizations to reduce the rampal1l prevalence ofrnsubstance abuse and lheir adverse impacts are diametrically incompatible with the magnitude ofrnthe problem. Therefore, on the basis of Ihe findings, the researcher recommends creating jobrnopportunities, increasing awareness and recreational facilities, and avoiding stigma andrndiscrimination towards youth substance abusers and AIDS patients.