$eta$-1, 4-endoglucanase (EC 3, 2, 1, 4) was isolated and purified from Nicotiana tabaccum L. Var. Virginia 115 suspensin cultured cells. The molecular weight as estimated by Sephadex G-100 was about 14, 000. The optimum pH for activity was 5.4. The Km value for carboxymethyl cellulose was 0.18 mg/unit and the enzyme was quite resistant to heating. Polyamine did not affect the activity of $eta$-1, 4-endoglucanase in vitro but the activity increased drastically when polyamines were added in the suspension culture medium. It is suggested that increase in $eta$-1, 4-endoglucenase activity due to polyamine might be related to growth of the plant.