This paper presents experimental results concerning the response of plain and straked circular cylinders. The isolated cylinders are mounted in a two degrees of freedom elastic base. Two straked cylinders are tested and they have the same pitch p = 10d and two different heights h = 0.1d and h = 0.2d. The longitudinal and transverse amplitude responses and wake structures of plain and helically straked cylinders are compared. The wake visualization uses the stereoscopic digital particle image velocimetry (SDPIV) technique. Comparing to the plain cylinder response, the p = 10d and h = 0.1d strakes moderately reduce the maximum amplitude response, while the p = 10d and h = 0.2d strakes suppress the vortex-induced vibrations. The strake effectiveness is directly related to the strake height. The Reynolds number varies from 1000 up to 7500 in the experiments.

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