The buckling capacity of the cylindrical shells depends on two geometric ratios of L/R and R/t. However the effect of thickness variation on the behavior of the shells is more complicated and the buckling strength of them is sensitive to the magnitude and shape of geometric imperfections. In this paper the effects of thickness variation and geometric imperfections on the buckling and postbuckling behavior of cylindrical shells are experimentally investigated. The obtained results are presented under the effect of uniform lateral pressure. It is found in this investigation that the buckling mode can be generated in the whole length of the shell, if the thickness variation is low.