Studies on the structure and functions of membrane proteins are impeded by their lability, hydrophobicity, difficulty in purification and low yields. Human chemokine receptor 3 (CCR3) is a G protein-coupled receptor related to allergic diseases. A Triton X-100/PEG20000 two-phase system was employed for enrichment separation of CCR3 over-expressed in E. coli. Optimal CCR3 partitioning with partition coefficient around 8 was obtained at pH 7.0, ionic strength of 0.3 mol/kg and 3 h equilibration time. Total recovery of CCR3 reached 102 +/- A 15%, which was much higher than 32 +/- A 5% of the normally used ultracentrifugation method. The recovered CCR3 was finally purified by two chromatography steps giving a final protein of 87 kDa.