$eta$-1,3-Glucanase (EC 3.2.1.39), a potential pathogenesis-related protein, was purified from soybean leaves. The enzyme was induced 7-fold in leaves after treatment of 40-day-old soybean plants with 10 nmol/l ethylene for 30 h. The enzyme was extracted from ethylene-treated soybean leaves in 50 mM sodium citrate (pH 5.0), and then purified in order by ammonium sulfate precipitation, DEAF-Sephadex A-50, CM-cellulose, and Sephadex G-75 chromatography. Two types of $eta$-1,3-glucanase, basic and acidic, were discriminated by DEAF-Sephadex chromatography, and only basic $eta$-1,3-glucanase was purified further. The basic $eta$-1,3-glucanase was purified 10-fold with a yield of 10.3%. The purified enzyme gave a single band on SDS-PAGE, and its apparent molecular weight was 33 KD. The enzyme showed optimum pH of 5.5 and broad pH stability, and showed optimum temperature $50^{circ}C$ and thermal stability below $50^{circ}C$. $K_m$ and $V_{max}$ values of the enzyme were 5mg/ml and 67 nmol glucose equivalent/min, respectively, for laminarin as a substrate. $eta$-1,3-glucanase was significantly inhibited by 10 mM $Cu^{2+}$, $Hg^{2+}$, and $Pb^{2+}$.