A NATO Advanced Research Workshop entitled New Methods for the Study of Molecular Aggregates was held at Tbe Lodge at Kananaskis Village, Alberta, Canada from 16 -20 June 1996. In fact the meeting was entirely concerned with the problem of analyzing biomolecular complexes, so the title of these proceedings has been altered to give a more precise description of the content. Tbe workshop was hosted by the time-of-flight group of the Department of Physics at the University of Manitoba, and was attended by 64 participants from around the world. '!venty-one invited talks were given and 27 papers were presented as posters. Of the 48 contributions, 22 papers (12 orals, 10 posters) are included in these proceedings. Tbe subject of the conference was the investigation of noncovalent biomolecular complexes, with particular focus on the application of mass spectrometry to their characterization. '!vo new ionization techniques introduced in the late 1980s, electrospray ionization (ES I) and matrix-assisted laser desorptionlionization (MALDI), resulted in a breakthrough in mass spectrometry, enabling its use in molecular weight and primary structure determination of biopolymers larger than 100 kDa. Recently it has been discovered that ESI mass spectrometry mayaiso be used to characterize complexes containing noncovalent interactions, thus opening new perspectives for supramolecular chemistry. ESI mass spectrometry has the advantage that the sampie is introduced from a homogenous solution which can be maintained at near physiological conditions of pR, concentration, and temperature.