Circular tank with rotationally symmetric continuities or discontinuities in geometry of shells are very largely used for the digester, sedimentation tanks in the Wastewater Treatment Plants. The analysis of the circular tank that the wall thickness is constant and the boundary is either fixed or pinned edge are considerably practical and simple, because the coefficients for the resultant forces are available in the tables or charts of many texts. Obviously, rigorous equations and synthetical ways should be carried out for the analysis wherever the discontinuities in geometry, loading and monolithically connected edge are presented in the structural system. CYLTANK was developed for this purpose. The program is intended for the engineers with fundamental knowledge of shell geometry, theory of thin shells and modern technique of numerical analysis. This program was developed by Structural Department of Brown and Caldwell Consulting Engineers.