Technical Abstract: Cocaine-producing species of Erythroxylum have been cultivated in South America for centuries, yet little is know of environmental effects on alkaloid production in these species. Given the high incidence of UV radiation in the equatorial and high altitude environments in which cocaine-producing species of Erythroxylum are cultivated, the present study was conducted to determine the effects of UV-B and UV-A radiation on alkaloid production in the cocaine-producing species Erythroxylum novogranatense var. novogranatense. Plants were grown in the field under shelters that were transparent to UV radiation (+UV-B & +UV-A) or filtered the UV-B (-UV-B & +UV-A) or both the UV-B and UV-A (-UV-B & -UV-A) portion of the solar spectrum. The treatments had no significant affect on plant biomass, specific leaf weight, or cocaine and trans-cinnamoylcocaine levels in the leaves. Absorption values in the UV region of acidified-methanol leaf extracts were higher for plants grown under the +UV-B & +UV-A treatment as compared to the -UV-B & -UV-A treatment. The alkaloid cis-cinnamoylcocaine decreased in the leaves of plants grown under the +UV-B & +UV-A treatment as compared to the -UV-A & -UV-B treatment. The truxillines, dimmers of cinnamoylcocaine, increased in leaves of plants that grew under both the -UV-B & +UV-A and the +UV-B & + UV-A treatments as compared to the -UV-B & -UV-A treatment. The results support the hypothesis that UV radiation is involved in the formation of truxillines from cinnamoylcocaines.