The quantification of large periodic loads caused by horizontal-axis wind turbines is a first step in the design of towers and foundations for wind energy conversion systems (WECS). This paper attempts to indicate by numerical examples that the choice of turbine blade profile is not critical in a preliminary system design stage and that certain assumptions of blade geometry lead to adequate load assessments at that stage. Also, a comparison of loads calculated with those obtained experimentally in the case of a large (0.8 MW) aerogenerator shows close agreement. © 1986.