Updated project metadata. We used stable isotope labelling of amino acids in cell culture coupled with high throughput quantitative mass spectrometry to analyse the protein composition of highly purified wild type adenoviruses, mutant adenoviruses lacking an internal protein component (protein V) and recombinant adenoviruses of the type commonly used in gene therapy including one virus which had been used in a clinical trail. We found that the viral protein abundance and composition was consistent across all types of virus examined except for the virus lacking protein V which also had reduced amounts of another viral core protein, protein VII. In all the samples analysed we found no evidence of consistent packaging or contamination with cellular proteins. We believe this technique makes a powerful method to analyse the protein composition of this important gene therapy vector and genetically engineered or synthetic virus like particles.