With a favorable result, we applied Sepharose CL-2B column to the isolation of ribosomal subunit, 50S, from P. Vulgaris cells. This report presents a simple and useful method for preparative separation of subunit species.Ribosomal preparation 225mg (wet wt.) was loaded on Sepharose CL-2B column (inner diameter 20 mm, gel column height 46 cm) which had been previously equilibrated with pH 7.5 Tris-buffer containing Mg2 + O.OOlM and KCl 0.1M. The column was developed with the same buffer. Elution was carried out with a flow rate of 12 ml/h. The adsorbance of the eluate was measured at 258hm. Two peaks were obtained in elution development. The result was checked up to be identical with that observed in ultracentrifuge analysis.According to the proteins contained, the percent recovery of subunit species was 91% in approximate estimation.