A reversed phase HPLC analysis of atorvastatin (AS) standard solution was performed using diclofenac (DF) as internal standard. Column oven temperature, flow rate and the composition of the mobile phase were varied in order to determine a practical system setup using a C18 column and UV detector. Two C18 columns of different length were compared regarding their influence on the AS peak shape. Based on these preliminary experiments a validation study was performed utilizing a C18 column at $62^{circ}C$ with a mobile phase consisting of sodium phosphate buffer (0.05 M, pH 4.0), methanol and acetonitrile (40:50:10, v/v/v). The detection limit for AS was $0.1{mu}g/ml$ and inter- and intra-day calibration curves were linear over a concentration range of $0.2-50{mu}g/ml$. Accuracy and precision were satisfactory in the AS concentration range of $0.5-50{mu}g/ml$.