OBJECTIVES: Our objectives were to investigate: 1) whether methods and reporting of published cost-utility analyses (CUAs) have improved over time; and 2) whether quality is higher in journals that published more CUAs. METHODS: A systematic search of the English-language medical literature identified 522 original CUAs published from 1976 through 2001. Each study was independently audited by two trained readers for a core set of data elements on study methodology and reporting, and a subjective assessment of overall study quality on a scale from 1 (low) to 7 (high) - data available at: http://www.hsph.harvard.edu/cearegistry/. High-volume journals were defined as those publishing 4 or more CUAs from 1976-2001. This study updates our previous analysis, which examined the quality of CUAs from 1976 to 1997. RESULTS: Several key elements improved over time. Comparing the 1998-2001 period (n=294) to 1976-1997 (n=228), articles improved in: clearly presenting the study perspective (73% vs. 52%, p<0.001); performing sensitivity analyses (93% vs. 89%, p=0.092); discounting both costs and QALYs (82% vs. 72%, p=0.016); and calculating and reporting incremental ratios (69% vs. 46%, p<0.001). More studies in the latter period took the societal perspective (30% vs. 23%). The overall quality score improved as well, though the change was not significant (4.25 vs. 4.10, p=0.19). The proportion of studies disclosing funding sources did not change (64% vs. 65%, p=0.88). Average quality score is greater in higher- vs. lower-volume journals (4.5 vs 3.7, p<0.001). CONCLUSION: Published CUAs have improved over time, though many still omit basic elements. Clinical journals, particularly those with little experience publishing CUAs, need to adopt and enforce standard protocols for conducting and reporting.