A hydrophobic interaction HPLC method was developed and validated for the analysis of human growth hormone (hGH) preparations. Separations were carried out on a TSK-Phenyl 5PW column using a descending linear gradient of 100% 1M ammonium phosphate dibasic/n-propanol (99.5:0.5), pH 8.0 to 100% 0.1M sodium phosphate/n-propanol (97.5:2.5), pH 8.0 over 30 minutes. The method proved highly reproducible for retention times, peak areas and peak heights, and the detector response for the main peak was linear between 1 and 1000 μg hGH/mL. Under these conditions, several hGH variants were resolved from the main hGH peak. A number of hGH preparations including the first WHO International Standard for hGH of pituitary origin and the new International Standard for hGH of recombinant origin were analysed.