Stimulant/amphetamine use presents a major public health problem. There is a dearth of research which has studied this behavior from a dual systems model perspective. This study examined the relevance of sensation-seeking and impulse control for predicting stimulant/amphetamine use and tested whether these relationships varied as a function of time. The Pathways to Desistance data were used in analyses, comprising the responses of 1,354 justice-involved youth across 84 months with 11 data points each. Mixed effects modeling was used to examine these relationships. Results indicated that greater sensation-seeking was associated with greater odds of stimulant/amphetamine use. This relationship varied as a linear function of time, with the salience of sensation-seeking for predicting stimulant/amphetamine use declining as participants got older. However, this interaction only reached marginal significance at the p < .09 level. Interventions focused on sensation-seeking may help reduce stimulant/amphetamine use, but effects may be greater for adolescents relative to young adults.