EN
Subject of the paper is the problem of predicting sea-going ship resistance and/or horsepo-wer in real operating conditions. Attention is drawn first of all to the need and possibility of revising the very much outdated but still used "service margin" method, which consists inadding an arbitrary percentage margin to the value of resistance or horsepower, relatively precisely determined for the calm water conditions. A negative impact in this respect isshown of the generally used delivery-acceptance procedures, where particular importanceis attached to the ship propulsion tests on the "measured mile". The need of revising the"service margins" is a consequence of an obvious need for most efficient ships from the technical as well aseconomic point of view. Secondly, it is a "must" of permanent improving the ship design quality - the adequacy and accuracy of design methods. The work presents the "wave service margin" coefficient models. It isassumed that they may contribute to the necessary rationalization of the procedure of real ship resistanceand/or horsepower determination. The work is based on the results of resistance tests of a series of ships designed within the Baltecologicalship project. The tests were carried out in the Chair of Ship Theory and Design of the Faculty of Ocean Engineering and Ship Technology, Gdańsk University of Technology