Recently, several liquid chromatographic methods for the assay of erythromycin base were developed and are being considered for the routine assay of erythromycin. In this study, we developed simple and rugged liquid chromatographic methods for the assay of erythromycin salts and esters, and used these methods for the assay of erythromycin estolate, erythromycin ethylsuccinate, erythromycin stearate, erythromycin gluceptate, and erythromycin lactobionate in bulk and pharmaceutical formulations. The HPLC methods proved to be simple, sensitive, versatile, and rugged. The developed methods provide an attractive alternative to current official microbiological methods. The HPLC assay results for all commercial erythromycin products tested comply with the USP Antibiotics-Microbial assay specification.