Anti-ribosomal P protein antibodies (Abs) recognize three specific ribosomal proteins located in the large ribosome's subunit. The term anti-ribosomal P protein Abs, often shortened in anti-P Abs, is due to the fact that these three proteins, P0, P1 and P2, of 38, 19 and 17 Kd molecular weight, respectively, are phosphorylated. One of the major points of interest of these autoAbs derives from their high specificity for systemic lupus erythematosus (SLE), their description in other connective tissue diseases (CTDs) being only occasional. In SLE patients, their association with renal and hepatic involvement has been proposed, while the possible association with psychiatric and/or neurological involvement is still a matter of debate. From a serological point of view, a preferential association of anti-P with anti-Sm and/or anti-DNA Abs, possibly due, at least in part, to cross-reactivity, has been suggested. This observation is intriguing since all these autoAbs are considered specific serological indicators of SLE. This review will summarize clinical and serological data on anti-P Abs provided by the main studies published in the last few years and the more recent findings about proteins constituting their targets.