Design wave height is an important parameter for evaluating forces on the coast and both onshore and offshore constructions. Extreme wave analysis was performed in order to evaluate the significant wave height for given return periods. Furthermore, the most probable distribution and range of spread parameter were defined for the Gulf of Trieste. All available data from buoys in the Gulf of Trieste and a ten-year set of results of the wave model WAM were obtained. A modified (corrected) data set of wave model results was used as input data for the extreme wave analysis. The calculated wave heights from the model underestimates measurements at the buoy. Therefore, it was necessary to modify the model results with correction factors, which are based on the wave climate. The model validation is based on structural relations between measured data on buoy Vida and the results of the wave model. In the thesis we describe the equations and procedures required for calculation of the significant wave height for a given return period. Moreover, the evaluation of the depth-limited maximum wave height is included. In addition, the thesis provides the wind and wave climate analysis for the Gulf of Trieste. The calculated return wave heights are the first estimates aimed for designers and construction contractors onshore and offshore in the Gulf of Trieste.