The current study was conducted with a sample of 253 college undergraduates to extend the findings in the existing research on motivational models of alcohol and marijuana use. Specifically it was intended to evaluate the relative benefits of assessing motives for using these drugs during a specific episode rather than in the dispositional fashion utilized in virtually every existing study on the subject. Affect regulation aspects of the motivational model were further explored by measuring state (rather than trait) affect immediately preceding a use episode. A timeline follow-back method was used to identify the most recent use episode and to assess recent quantity of use and negative consequences in greater detail. The similarity of the types of motives derived from episodic assessment to those seen dispositionally lends further credence to the validity of DUM subtypes, their distinct pathways to use and related problems, and the affective-motivational model as a whole. Affective states (rather than just traits) played a significant role in the motives endorsed and outcomes. Previous findings on the direct effects of drinking to cope on the development of problems were confirmed on an episodic level. Finally, episodic assessment appeared to have some utility above and beyond that of dispositional assessment when examining specific episodes of use. / Ph. D.