States were aggregated into the following categories: a moderate class where the maximum fine for first possession offense of a small amount of marijuana did not exceed $500; a severe class where States' maximum fines were above that amount; and a changing class comprising States in which the maximum fines dropped from severe to moderate in the period's second half. Analysis showed that use was lowest and grew most rapidly in the severe class States and was highest and grew less in the changing class. These results suggest that both the prolonged retention of severe penalties and their relatively high use levels from the beginning of the decade. A simultaneous analysis of time and age trends by class of States shows that use levels vary curvilinearly for the most part, with age alone as a causal factor rising from adolescence to young adulthood and dropping off again towards middle adulthood. This relationship is strongest in the moderate class and most qualified by time in the severe class. The lower age limit for relatively common use dropped throughout the study period, although the upper age limit appeared to be age 30. A concurrent analysis of trends in time and age with trends in the time of penalty moderation indicated that time of moderation does not significantly affect variations in marijuana use. To account for variations which do not follow the curvilinear age patterns, researchers must consider variables reflecting the heterogeneity in risk populations and legal regimes across the country. Graphs, charts, and five footnotes are included. (Author summary modified)