The tumor suppressor p53 is commonly mutated in human cancers. However, two homologs of p53, p63 and p73, are frequently overexpressed in tumors and are associated with tumor subtypes, clinical outcomes, and responses to therapy. There are many isoforms of p53, p63 and p73 (the p53 family). Proper detection of and discrimination between the members of this tumor suppressor family in human tissues is of critical importance to cancer research and clinical care. In this study, we assessed the specificity of several commercially available and newly generated p73 antibodies, focusing on antibodies that distinguish between the TA p73 and DeltaNp73 isoforms by western analysis, immunohistochemistry, and immunofluorescence. In addition, we found that the pan-p63 and pan-p73 antibodies tested cross-react with p73 and p63 respectively. The results of this study have important implications for analysis of p63 and p73 expression and co-expression in human tumors, and for potential use of these reagents in molecular diagnostics and therapeutic decision-making.