Background: cigarette smoking escalates most in early to middle young adulthood. However, little research has examined a range of multilevel factors in relation to smoking trajectories during this time. Methods: we examined: 1) trajectories of cigarette smoking among 2967 us college students (aged 1825) in a two-year, six-wave longitudinal study (using growth mixture modeling); and 2) intrapersonal- (i.E., Other substance use, depressive symptoms, adhd symptoms,); interpersonal- (i.E., Adverse childhood events, social support, parental tobacco and marijuana use), and community-level (i.E., Type of college, rural vs. Urban setting) predictors of differing trajectories (using multinomial logistic regression). Results: we identified three trajectory classes: 1) dabblers, who used cigarettes at one point in their life or not at all (85.6%); 2) College onset smokers, who began smoking regularly during the college years (6.2%); And 3) later onset smokers, who began smoking during the mid- to late-20 s (8.2%). Multinomial regression (with dabblers as the reference group) showed that predictors of being college onset smokers included being male (p =.031); Asian (p =.001) But not black (p =.008; Ref: white); early onset smokers (i.E., Initiation before age 15; p =.006); Past 30-day users of little cigars/cigarillos (p =.024), Alcohol (p <.001), And marijuana (p =.008); Children of tobacco users (p =.050); And public (p =.031) Or a technical college students (p <.001; Ref: private college); predictors of being later onset smokers were being male (p =.019) And technical college students (p =.005). Conclusions: despite some young adults smoking initiating/escalating in middle young adulthood, few risk factors were documented. This understudied period warrants greater examination to inform intervention. 2018 Elsevier b.V.