The MACRO underground experiment has started a systematic experimental
study of the structure of a very high multiplicity event sample, with
the aim of gaining a better understanding of the features of the high
energy showers. We present here two new analyses: a) the analysis of
the distribution of the separation between pairs of high multiplicity
muons (''decoherence'' function); b) the search for clusters of muons
within high multiplicity events. Tile first results are discussed toge
ther with a comparison between the real data and the Monte Carlo predi
ctions.