OBJECTIVE: To assess 1) the quality of reporting randomised clinical trials in dental (RCT-Ds) and medical research (RCT-Ms), 2) the quality of RCT reports in relation to the journal impact factor, 3) the source of funding, and 4) the quality of RCT-Ds in different areas of dental research. DESIGN RANDOM: samples of 100 RCT-Ds and 100 RCT-Ms published in 1999 were evaluated for quality of reporting under blinded conditions with the Jadad quality assessment scale. In addition, correlation between the quality scores and journal impact factor or source of funding, as well as area of dental research were analysed. RESULTS: The quality of RCT-Ds and RCT-Ms published in 1999 was generally inadequate. The quality was largely equivalent in RCT-Ds and RCT-Ms. There was no correlation between the quality scores and the journal impact factor or the source of funding. Some differences were found in the quality scores between different areas of dental research. CONCLUSIONS: The results from these RCT-Ds and RCT-Ms show that most of them were imperfect in the reporting of methodology and trial conduct. There is a clear need to improve the quality of trial reporting in dental and medical research.