A rapid, simple and efficient method to extract RNA from the adult polyps of a soft coral, marine cnidarian, Scleronephthya gracillimum $(Kddot{u}kenthal)$; was developed in this study. The highest yield and purity of RNA was obtained with the lysis solution containing 35 mM EDTA, 0.7 M LiCl, 7.0% SDS, and 200 mM Tris-Cl (pH 9.0). Approximately $40{mu}g$ of total RNA was extracted from 200 mg of liquid nitrogen-pulverized polyp tissue. The ratio of absorbance at 260 nm and 280 nm ranged from 1.8 to 2.0. The results of the reverse transcription polymerase chain reaction (RTPCR) with ${eta}-actin$ gene specific primers and Northern blot analysis using the same gene probe revealed that the RNA extracted by our method had high quality, and was sufficient for subsequent molecular biological analyses. This method was effective for RNA extraction from other soft coral species which belong to the genus Dendronephthya.