The effect of different treatments on the quality of agar produced from Pterocladia has been studied, and the conditions for the production of material of good quality have been standardized. In the modified process, sun-bleached seaweed was washed well in water, soaked for 24 h, and then ground to a pulp and rinsed again in water. The pulp was then extracted with water (weed-to-water ratio, 1:30) under pressure for 2 h after adjusting the pH to 6 by the addition of acetic acid. The agar gel, after freeze thawing, was bleached with NaClO before drying in a current of hot air. Pretreatment of the seaweed with alkali at 80°C for 2 h prior to extraction was found to improve the quality of agar to a very great extent.