The effect of cathodic protection on corrosion-fatigue strength in synthetic seawater was investigated for notched specimens of high-tension steels (HT50 and HT80). For slight notches (stress concentration factor, a_k≤2), fatigue strengths with cathodic protection were almost the same as those in laboratory air, because the cathodic protection retarded the formation of corrosion pits. When a_k was further increased, corrosion-fatigue strengths reached a value which is probably the fatigue strength of the circular cracked specimen. The value is higher than that in laboratory air due to the initiation of nonpropagating cracks. The fatigue strengths of welded specimens were compared with those obtained for the notched specimen.