In the current study, we quantified changes in the growth and alkaloid content of wild poppy, (Papaver setigerum) as a function of recent and projected changes in global atmospheric carbon dioxide concentration, [CO 2 ]. The experimental [CO 2 ] values (300, 400, 500 and 600μmol mol −1 ) correspond roughly to the concentrations that existed during the middle of the twentieth century, the current concentration, and near and long-term projections for the current century (2050 and 2090), respectively. Additional carbon dioxide resulted in significant increases in leaf area and above ground biomass for P. setigerum at all [CO 2 ] relative to the 300μmol mol −1 baseline. Reproductively, increasing [CO 2 ] from 300 to 600μmol mol −1 increased the number of capsules, capsule weight and latex production by 3.6, 3.0 and 3.7×, respectively, on a per plant basis. Quantification of secondary compounds (i.e. those not involved in primary metabolism) included the alkaloids morphine, codeine, papaverine and noscapine. The amount of all alkaloids increased significantly on a per plant basis, with the greatest relative increase occurring with recent increases in atmospheric carbon dioxide (e.g. from 300 to 400μmol mol −1 ). Overall, these data suggest that as atmospheric [CO 2 ] continues to increase, significant effects on the production of secondary plant compounds of pharmacological interest (i.e. opiates) could be expected.