A previously described isocratic liquid chromatographic (LC) method for the analysis of tetracycline on poly(styrene-divinylbenzene) allows the complete separation and resolution of tetracycline (TC), 4-epitetracycline (ETC), anhydrotetracycline (ATC) and 4-epianhydrotetracycline (EATC). By means of a half-fraction factorial design, the importance of the individual chromatographic parameters and parameter interactions of this LC method was examined. The influence on the retention of ETC, TC and EATC is measured. A mathematical regression model was derived which predicts retention times with good reliability. Both the retentions of ETC and EATC are strongly affected by chromatographic parameters and parameter interactions, which only slightly affect the retention of TC. Adequate combination of the most relevant of these parameters enables optimization of the chromatographic separation if necessary