Introduction: Actually the best way to review efficacy and safety or Randomized Clinical Trials (RCT) of any therapeutic intervention. Despite randomization (reported as most important way to ensure external validity), RCT have limitations, these could carry weight on its clinical applicability. Authors of this search described limitations reported originally by each RCT authors of 4 important journals. Methods: An observational and descriptive study with a total of 30 internal medicine trials as sample. All the trials published in the last 3 years in the most important journals. 11 categories of limitations were identifed and statistically analyzed with relative and absolute frequency. Outcomes: A total of 30 RCT were included in the revision. Were identified 11 categories of different limitations , in order of frequency: attributable to the intervention (16,3%), external validity by population (13,1%) , duration of follow-up (13,1%), co-intervention (11,4%), suspension of the intervention or withdraw of the participants during the study (11,4%),outcomes measurement (9,8%),trials without limitations (9,8%),sample size (6,5%), serious adverse events (4,9%), trials without placebo (1,63%), and limitation about trials methods (1,63%). Conclusion: In a total of 30 RCT, the most frequent limitation is attributable to the intervention followed by external validity.