Graffi S., Unguendoli F. Resonant Harmonic Oscillators and Eigenvalue Multiplicity (40K, LaTeX) ABSTRACT. Explicit formulas are worked out for the eigenvalue multiplicity of a system of $n$ independent quantum harmonic oscillators in the general case of $1\leq s\leq n-1$ resonance relations among the frequencies $\om_1,\ldots,\om_n$. As a particular case we prove that, even though the quantum numbers are always less than the degrees of freedom, the \ev s are in general intrinsically degenerate only in the completely resonant case $s=n-1$.