Interactions of 16O and 32S at 200 GeV per nucleon in emulsion and in emulsion-tungsten chamber targets were tagged by transverse energy and multiplicity triggers in the HELIOS apparatus at CERN. As a first sample, 375 events, covering a wide range of transverse energies, were located and studied in emulsion. Results are reported in this paper. The angular distribution has been measured, event by event, with a wide pseudorapidity coverage, both in emulsion and in the HELIOS calorimeters. The total charged multiplicity and the transverse energy per charged particle have been obtained as a function of the transverse energy and of the pseudorapidity. The measured distributions are compared with the predictions of the Dual Parton Model, as coded in the IRIS generator. Assuming that 59% of the ET is transported by charged particles, and estimating the energy density by a full transparency picture, a comparison with cosmic-ray data has also been attempted.