OBJECTIVES Targeted therapies using pharmacogenomic data promise to improve the safety, efficacy, and cost-effectiveness of drug treatment significantly. To assess research progress in targeting biopharmaceutical interventions to address unmet medical need, we investigated therapeutic, temporal, and economic trends in personalized medicine using data from a national clinical trial registry. METHODS Personalized medicine (PM) is the use of a patient's genotype or other molecular diagnostic (pharmacogenomic) data to guide a treatment decision. We queried ClinicalTrials.gov for studies using pharmacogenomic criteria for inclusion or exclusion, or for stratifying outcomes, restricting our analysis to Phase III or IV studies initiated on or before January 7, 2009. We verified the sensitivity of our search strategy using a known set of studies for which PM-related trials have been conducted. RESULTS As a result, 1.7% (N=155) of registered Phase III/IV trials in the US (N=9,111) used pharmacogenomic data. Over time, the number of trials using pharmacogenomic data has increased greatly and, as expected, most PM trials (55%) were in the therapeutic areas of oncology and hematology. However, we observed a marked increase in the number of PM trials for drugs targeting disorders with highly variable treatment response, such as neurology and mental health disorders including Alzheimer's, depression, and schizophrenia. In addition, we found that the source of funding for PM trials increasingly comes from the pharmaceutical industry rather than from public sources. CONCLUSIONS Targeting drugs to smaller subgroups is assumed to result in treating those patients most likely to respond and least likely to experience an adverse event. These data are consistent with the idea that these gains will be experienced broadly across therapeutic areas, however, the degree of impact will vary according to our understanding of the molecular basis of disease, with associated implications for assessing relative clinical and cost effectiveness.