This paper presents a closed-form solution of the problem of free beam-type vibration of a long cylindrical shell subject to uniform axial tension, uniform internal pressure, and elastic axial restraint. The shell is assumed to be clamped at the ends. The bending moment-curvature relationship employed in this paper is non-linear due to the effect of ovalization (flattening) of initially circular cross sections. Another non-linear effect taken into account is the stretching of the shell axis which is caused by the axial restraint. The analysis results in a cubic differential equation; the frequency of the solution of this equation is found exactly using elliptic integrals. © 1987.