Growing concern within Congress, the pharmaceutical industry, and the Food and Drug Administration (FDA) over the excessive time and cost required to develop new drugs and bring them to market has led to several initiatives designed to speed the drug development process, e.g., the Prescription Drug User Fee Act of 1992 and recent efforts at legislative reform of the agency. To assess the impact of these initiatives, it is useful to examine recent trends in new drug development and review. This report is the fourth in a series in which we analyze new chemical entities (NCEs) recently approved by the FDA. In 1993, 1994, and 1995, the FDA approved 75 new drugs, 67 of which met the Tufts Center's definition of an NCE. Of the 67, 31 (46%) received priority review, 13 (19%) had orphan drug status, and 5 (7%) were approved under the accelerated approval regulations. For the 67 NCEs, the mean length of the clinical phase (investigational new drug filing to new drug application submission) was 7.1 years, and the approval phase (new drug application submission to approval) was 2.0 years. The mean approval phase for the 31 priority NCEs (1.5 years) was 38% shorter than that for the 36 standard NCEs (2.5 years). Compared with similar values for the previous 3-year period, the mean clinical phase for all NCEs increased by 16%, whereas the mean approval phase decreased by 23%. Of the 66 NCEs for which foreign marketing data were available, 34 (52%) were available in foreign markets one or more years prior to U.S. approval, with a mean of 7.7 years of earlier foreign marketing.