The motion of a mathernatieal pendulum whose point of suspension performs small-amplitude horizontal harmonic oscillations
is considered. The non-integrability of the equation of motion of the pendulum is established. The periodic motion of the pendulum
originating from a stable: position of equil~rium is obtained and its stability is investigated. Unstable periodic motions originating
from unstable positions of equil~rium are indicated and the separatrice surfaces asymptotic to these motions are determined.
The problem of the e~Itence and stability of periodic motions of the pendulum originating from its oscillations with arbitrary
amplitude and rotations with arbitrary mean angular velocity is investigated.