Questions concerning data quality and reproducibility of proteomic laboratories spurred the ABRF-PRG group to design a study to systematically assess the reproducibility of proteomic laboratories. Sixty four participants were recruited from the broader mass spectrometry community and were asked to analyse provided aliquots of a digested 6 bovine protein mixture every month for a period of nine months. Data were uploaded to a central repository and the operators answered an accompanying survey. Forty five laboratories submitted a minimum of 8 data-dependent acquired LC-MSMS raw files No standard operating procedures were enforced; rather the participants were encouraged to analyse the samples according to usual practices in the laboratory. Unlike previous studies, this investigation was not designed to compare laboratories or instrument configuration; but rather to assess the temporal intra-laboratory reproducibility. The outcome of the study was reassuring in that 80% of the contributing laboratories were performing analyses at a medium to high level of reproducibility and quality. For the groups that had one to several outlying data sets, the major contributing factor that was correlated via the survey data was the preponderance of a preventative maintenance prior to the LC-MSMS analyses. Thus suggesting that laboratories should closely scrutinise the quality control data following such events.