To assess the transparency of assisted reproductive technology (ART) surveillance reports published by the Centers for Disease Control and Prevention (CDC) and by the Society for Assisted Reproductive Technologies (SART). Retrospective analysis. Private clinical ART and research center. We analyzed ART data for the years 2005-2010, which were reported under federal mandate to the CDC (818,927 completed cycles) and voluntarily to SART (812,400 initiated cycles). None. Initiated cycles excluded from final outcome reporting were used to evaluate transparency. Only SART, but not CDC, reported initiated cycles, allowing analysis of excluded cycles. Excluded cycles increased significantly from 3.3% to 7.4% between 2005 and 2010. By 2010, 13/341 (3.8%) ART centers accounted for 50% of excluded cycles, representing an average of 37.3% of their cycles. These 13 clinics reported significantly better pregnancy and cancellations rates than national averages and collectively increased by 19.9% their share of U.S. ART cycles. Our data indicate decreasing transparency in public ART reporting in the United States, likely due to changes in practice and reporting patterns. A few clinics accounted for the majority of excluded cycles, leading to improved reported clinical outcomes and increasing market share. CDC and SART should ensure that all ART clinics publicly report the outcomes of all initiated cycles including embryo-banking cycles. ART surveillance and quality of care may be improved by prospectively tracking the total reproductive potential of each initiated cycle.