  We study the multiquark hadrons in large $N$ QCD under the 't-Hooft limit,
extending Witten's picture of the baryons. We explore the decay widths of
tetraquarks, pentaquarks and dibaryons. Based on the decay behaviors, we point
out in the $N\to \infty$ limit decay widths of tetraquarks stay constant, while
those of pentaquarks and dibaryons above certain thresholds can diverge. In the
large $N$ limit, we find that the ground states of the three spectroscopic
series are stable or narrow and that the excited states of pentaquarks and
dibaryons above the indicated thresholds are not observables. We compare our
results with those obtained in a different large $N$ generalization of
tetraquarks.
