Oncology accounted for the most registered clinical trials as of Nov. 1, 2007, according to a recent review of U.S. trials data on ClinicalTrials.gov. The analysis, conducted by Nature Reviews, examined two years of data for industry-sponsored phase II through phase IV trials, including trials that were first registered between October 2005 and September 2007. Oncology, central nervous system disorders, cardiology, infectious diseases, endocrinology and respiratory diseases accounted for almost two-thirds of all protocols and more than two-thirds of all sites. Rheumatology saw the highest relative growth in the number of trials, making rheumatoid arthritis the third most common disease for clinical trials.