Abstract:The study investigated the prevalence of substance abuse and its prediction by parenting styles and peer pressure among university students. Participants in this cross-sectional survey consisted of four hundred and fifty two randomly selected undergraduates of Olabisi Onabanjo University (OOU), Ago-Iwoye. The sample consisted of 221 (48.9%) males and 231 (51.1) females. Participants' age ranges were as follow: 126 (27.9%) were aged between 18 and than 20 years, 312 (69.0%) were aged between 20 and 25 years while 14 (3.1%) were aged between 25 and above. Students who were younger than 18 years were excluded from participating in the study. Results indicated that about 47% of all respondents reported current use while 58% reported lifetime use of one or more psychoactive substances. Prevalence rates of use of all categories of drugs by respondents are presented in Table 1. Life time prevalence rate was highest for alcohol (43.14%), followed by tobacco (37.61%), stimulants (22.57%), cannabis (18.14%), sedatives (17.92%) and heroin (12.17%). parenting styles (permissive parenting, authoritarian parenting and authoritative parenting), peer pressure and sex jointly predicted substance abuse among students (R = .48; F = 9.16; p<.01) by accounting for 23% of the variances in substance abuse. The study highlighted the important roles of parenting styles (especially authoritative parenting), peer pressure, age and gender in understanding students' substance abuse problem. The study concluded that these variables should be factored into intervention programmes aimed at stemming the tides of substance abuse among university students. It is also important for relevant interventions to commence before students enter the university since many young people come to the university or college with pre-existing perceptions and expectations concerning substance use, and often start university with already established habits and orientations.