Results are presented of an experimental and analytical study of the longitudinal vibrational response of a modified Agena-B vehicle. The empty, unpressurized vehicle was excited with sinusoidal loads and the response was measured through a frequency range including the first two classical longitudinal. modes of the structure. Non-axisymmetric shell response (shell vibration modes) was noted extensively during the experimental tests. Comparison of the analytical and results indicates that a one-dimensional analytical model gave good results in comparison with experimental results. / Master of Science