A technique has been developed to evaluate the dynamic pressures on cylindrical structures due to irregular waves based on McCamy and Fuchs linear diffraction theory and principle of superposition. Experiments have been conducted in Hydraulic Engineering Laboratory, Indian Institute of Technology, Madras to examine the dynamic pressures excited by irregular waves on circular cylinders of large diameter. The pressures around the cylinder at representative locations were measured and compared with calculated pressures. The spectral density functions computed from pressure time series measured in the laboratory agree well with the calculated pressure spectral densities. The agreement is good and encouraging. © 1983.