Baclqground; Pathological interner use may lead to serious psychosocial problems and dysfunction. Obrectives: The purpose of the study was to investigate the prevalence of pathological intemet use among trndergladuate university students in five ASEAN countries in relation to sociodemographics, intemei use variables, psychosocial factors, and comorbid symptoms. Methods: In a cross.sectional survey in 2015 in Indonesia (Yogyakarta),Malaysia(Kuala Lumpur), Myanmar(Yangon),Thailand (MahaSarakham), and Vietnam (Hanoi),3240 undergraduate university students (Mean age = 20.5 years, SD = L6), who were randomly selected,responded to aquestionnaire includingthe "YoungDiagnostic QuestionnaireforlnternetAddiction"(YDQ) and othermeasures. Xesults: overall, the prevalences of pathological internet use were 35.9x (ranging from 16.l% in Myanmat to 52.4% in Thailand), maladaptive use 34.8X and adjusted Internet us€rs 29.9%. In multivariate logistic regression analysis, internet use variables (heavy overall Internet use, heavy Internet use for recreational purposes, and heavy smarq>hone use), psychosocial factors (the experience ofchildhood physical abuse, childhood sexual abuse, lack ofsocial support, and poor academicperformance), and comorbid symptoms (having a self<lassified gambling problem, hazardous or harmful alcohol use, past u-month drug use, severe depression, sleeping problems, having attempted a suicide, and PISD symptoms) were found to be associated with pathological internet use. Concluslons: The studyfoundaveryhigh prevalence ofpathologicalinternet use; those studentslackingpsychosocialsupportand having comorbid symptoms were at the highest risk