In the general periodic inspection diagnosis of cathodic protection applied to marine steel structures, we can get quantitative information as an index called "potential" instead of a qualitative index (deterioration degree a, b, c, d) as in the case of visual inspection. However, there are few cases where the inspection and diagnosis results are generally published. The same applies to the detailed inspection and diagnosis of cathodic protection (anode consumption, current from anode, etc.). If this information is made public and shared, it will be possible to carry out inspections and diagnoses related to cathodic protection more efficiently. Furthermore, it can be used as a reference material when developing new technologies related to inspection and diagnosis.
　In addition, there is a theoretical correlation between the potential (E) and the current from anode (I). It has been pointed out that the amount of anode consumption (usually grasped by diver), that is, the remaining life of the anode can be estimated from the potential with a certain degree of accuracy. However, there are few cases where the estimation accuracy has been verified.
　Based on the above, with the main purpose of contributing to the sophistication and labor saving of cathodic protection inspection and diagnosis, and publicizing and sharing the results of inspection and diagnosis, various inspection items related to cathodic protection have recently been regularly inspected. First, the diagnosis results were organized. Furthermore, the results of the additional surveys were summarized. The main findings obtained from this study are shown below.
1) The actual conditions of inspection and diagnosis results regarding cathodic protection in jacket-type structures and steel pipe pile-type piers are shown.
2) In the jacket-type structure (Haneda Airport D runway), about 1500 anode mounting conditions were confirmed after 5 and 10 years, respectively. There was no dropout of the anode. In addition, in the sheet pile type structure, the case where the anode dropout could be grasped by the potential measurement was shown.
3) Similar to the previous findings, most of the relationships between the potential and the current from anode in this case simultaneously satisfied the assumed values at the time of design. This result also suggests that it may be possible to judge that the anode life satisfies the design service life of the anode if the potential falls below a certain threshold value.

Key Words: Marine environment, steel structures, cathodic protection, periodical inspection