This study was conducted to screen in vitro angiotensin - I converting enzyme (ACE) inhibitory activities of methanol (MeOH) and aqueous extracts at 20°C and 70°C, respectively, prepared from twenty-six red algae obtained from the coast of Jeju Island in Korea. Among aqueous extracts at 20°C (20AE) from red algae Lomentaria catenata showed the strongest ACE inhibitory activity and Lithophyllum okamurae recorded the second highest activity. From MeOH extract at 20°C (20ME) Ahnfeltiopsis flabelliformis possessed the strongest ACE inhibitory activity. Remarkable activities from MeOH extracts at 70°C (70ME) were observed in Grateloupia filicina, Sinkoraena lancifolia and Grateloupia lanceolata. However, no significant activity was found in aqueous extracts at 70°C (70AE). The IC50 values, which are concentrations required to inhibit 50% activity of ACE, for ACE inhibitory activities of 20AE from Lithophyllum okamurae and L. catenata were 13.78 and 12.21 μg mL?1, respectively. The IC50 values of 20ME from A. flabelliformis and Laurencia okamurae were 13.84 and 106.15 μg mL?1. Those of the 70ME from Bonnemaisonia hamifera, Grateloupia filicina, Sinkoraena lancifolia, G. lanceolata, Gracilaria vermiculophylla and L. okamurae ranged from 25.82 to 124.69 μg mL?1.