A field permeability test (FPT) apparatus and method were developed and evaluated in both the laboratory and the field. The developed prototype FPT apparatus and method were used in the testing and evaluation of in-service marine structures in conjunction with other standard tests. The developed FPT apparatus and method appear promising in providing a suitable measuring system for the rapid, convenient, and reliable determination of the in situ water permeability of structural concrete. There appears to be a linear relationship between the charge (in coulombs) passed through a concrete material as measured by the rapid chloride permeability test (AASHTO T277-83) and its corresponding water permeability, with a coefficient of determination, R squared, of 0.90. There was an apparent relationship between permeability and durability of concrete in service. The concrete material that exhibited durability problems also demonstrated high permeability. The FPT method was demonstrated to be able to provide a relative measurement of permeability that can be used as an indication of the quality and performance characteristics of structural concrete.