Microsequencing of proteins recovered from two-dimensional (2-D) gels is being used systematically to identify proteins in the master human keratinocyte 2-D gel database. To date, about 250 protein spots recorded in human 2-D gel databases have been microsequenced and, of these, 145 are recorded in the keratinocyte database under the entry partial amino acid sequence. Coomassie Brilliant Blue-stained protein spots cut from several (up to 40) dry gels were concentrated by elution-concentration gel electrophoresis, electroblotted onto PVDF membranes and digested in situ with trypsin. Eluting peptides were separated by reversed-phase HPLC, collected individually and sequenced. Computer search using the FASTA and TFASTA programs from Genetics Computer Group indicated that 110 of the microsequenced polypeptides shared significant similarity with proteins contained in the PIR, Mipsx or GenEMBL databases. Only 35 polypeptides corresponded to hitherto unknown proteins. Peptide sequences of all 145 proteins are listed together with their coordinates (apparent molecular weight and pI) in the keratinocyte database.