OBJECTIVES: Inadequate reporting of continuous outcomes is a major problem while performing meta-analysis. The objective of this study is to estimate the nature and scale of inadequate reporting of continuous outcomes. METHODS: Reporting quality of continuous outcomes (baseline, endpoint and change from baseline data) was analysed across four disease area reviews conducted in lipid disorder, overactive bladder, multiple sclerosis and rheumatoid arthritis. Reporting quality was considered inadequate when either number of patients analysed (N) was not reported or error term was missing/could not be calculated from the reported statistics. Analyses were conducted using STATA 9.2. RESULTS: In total 12,236 reported outcomes across the four systematic reviews were included in the analysis. Inadequate reporting of continuous outcomes was frequent and observed for 3912 (31.97%) outcomes. The estimate of inadequate reporting varied across selected reviews and ranged from 27.10% to 45.77% in lipid disorder and overactive bladder, respectively. Of the outcomes reported inadequately, number of patients analysed (N) was missing for 8.82% whereas error term was missing or could not be calculated for 91.18% outcomes. When the reporting quality was analysed by the outcome type, it was observed that change from baseline data were often reported inadequately (49.63%) compared to baseline & endpoint data (25.00% and 24.51%, respectively). CONCLUSIONS: Inadequate reporting of continuous outcome was frequently observed among the selected reviews especially for the change from baseline outcomes. The results demonstrated that for majority of the outcomes, the error term was either missing or could not be calculated from the given statistics. This inadequacy of reporting could have a significant impact on the results of meta-analysis. Our results are indicative of outcome reporting bias which needs to be investigated further.