Domestic seaweeds Gracilaria verrucosa collected from coastal areas of Namhae, Wando and Yeosoo, Korea were subjected to the examination of yield and quality of agar prepared according to various pretreatment conditions. In alkali treatment at high temperature, higher alkali concentration for one-hour period at $90^{circ}C$ gave rise to higher yield of agar. In acid treatment, higher yield was obtained by higher acid concentration and longer treating period. Alkali treatment at room temperature gave rise to a slightly decreased yield at higher alkali concentration and longer treating time. Total nitrogen and crude ash of agar samples were greatly decreased by pretreatments. Jelly strength, gelation ability, gelation point and viscosity of agar samples tended to increase as the alkali-treating condition of seaweed became stronger. It was shown that sulfur content of agar had a high negative correlation with jelly strength of its gel. Various alkali treatments of seaweed at room temperature showed no marked difference in agar quality and did not exhibit any good effect comparable to alkali treatment at high temperature.