The 14-3-3 proteins constitute a family of highly conserved and broadly expressed multifunctional polypeptides that are involved in a variety of important cellular processes that include cell cycle progression, growth, differentiation as well as apoptosis. Although the exact cellular function(s) of 14-3-3 proteins is not fully elucidated, as a rule these proteins act by binding to protein ligands, thus regulating their activity; so far more than 300 cellular proteins have been reported to interact with 14-3-3 proteins. Binding to cognate interacting partners is isoform-specific, but redundancy also exists, as several binding peptides can be recognized by all isoforms, and some functions can be carried out by any isoform indistinctly. Moreover, by interacting with different ligands in a spatially and temporally-regulated fashion the same isoform can play multiple maybe even opposing roles, where the resultant cellular outcome will be determined by the integration of the various effects. Although there is a large body of literature on specific aspects of 14-3-3 biology not much is known on the coordinated aspects of 14-3-3 isoform expression, post-translational modifications, and subcellular localization. To address the question of isoform-specific differences, we carried out a comparative analysis of the patterns of expression, phosphorylation, and subcellular localization of the 14-3-3 , , , and protein isoforms in transformed human amnion cells (AMA). To validate as well as broaden our observations we analyzed the occurrence of the various isoforms in a large number of established cell lines and mammary and urothelial tissue specimens. Given the systematic approach we undertook and our application of isoform-discriminating technologies to the analysis of various cellular systems, we expect the data presented in this study to serve as an enabling resource for researchers working with 14-3-3 proteins.