Return wave heights at eleven NOWPHAS stations along the Japan Sea coast were estimated through the regional frequency analysis with the L-moments method. Several plotting position estimators have been examined through large-scale Monte Carlo simulations, and the estimator with α = 0.45 and β = 0 has been recommended for application. Eleven stations were divided into two regions to maintain homogeneity of the data within the regions. The wave data in the two regions were well fitted by the Weibull distribution with the scale parameter of 1.202 and 1.224. The 100-year significant wave height H100 varied from 8.37 m at Tottori to 10.74 m at Sakata. The Generalized Pareto (GPA) distribution also exhibited good fitting to the wave data with the estimated H100 varying from 7.68 m at Tottori to 9.84 m at Sakata, but H100 at five stations (Setana, Fukaura, Sakata,Niigata, and Hamada) was lower than the maximum significant wave height observed there.
