An overview of previous large-scale studies identifying yeast proteins. The studies using a combination of two-dimensional gel electrophoresis and mass spectrometry (2DE) are Shevchenko et al. , Garrels et al.  and Perrot et al. . Experiments using only MS or 1D PAGE and MS (LC/MS) are Washburn et al. , Peng et al.  and Wei et al. . The Wei et al. study is colored in grey and has a question mark because no data were provided on the identifications, making it difficult to evaluate the claim of 3,019 identified proteins, especially as low resolution mass spectrometry was employed.