Immunoblotting is widely utilized to evaluate the presence of antigens of interest in various biological samples, monitor antigen purification, assess epitope retention after antigen degradation, or assay for the presence of antibodies of a particular specificity in biological fluids [reviewed in Refs.(1–4)]. Under certain circumstances, eg, if a blot suggests an unexpected difference in antigen expression between two samples or the antigens being analyzed are derived from a precious source, it can be important to sequentially probe the same blot for the presence of multiple antigens. The present study demonstrates that treatment with sodium azide after detection of bound HRP1-coupled secondary antibodies results in inhibition of the reporter group, thereby facilitating sequential probing of blots if reagents raised in multiple species are available.