  We set up a suitable renormalization programme for the one-loop computation
of the decay rate Gamma(H==>hh) in the Minimal Supersymmetric extension of the
Standard Model. We then perform an explicit diagrammatic calculation, including
the full contributions from top, bottom, stop and sbottom loops. We find that,
for tan(beta) close to 1, and m_H greater than or approximately equal to 2 m_t,
the results can significantly differ from those previously obtained in the
effective potential approach. However, the latter method remains a good
approximation in the region of parameter space which is most relevant for H
searches at large hadron colliders.
