Adriaan Blaauw; Emeritus Professor of Astronomy at the Universities of Groningen and Leiden, former Directo.r of the Kapteyn Laboratory and of the European Southern Observatory, celebrated his 70th anniversary on 12 April 1984. To mark this event, an international Symposium was con- vened on the subject "Birth and Evolution of Massive Stars and Stellar Groups", a subject which has played the leading role in Blaauw's scien- tific research. The present volume contains the Scientific Proceedings of that Symposium. The meeting was organized by a Committee consisting of: W.H.W.M. Boland (Secretary), W.N. Brouw, W.B. Burton, E.P.J. van den Heuvel, H. van der Laan and H. van Woerden (Chairman). Together, these six persons represented the Executive Committees of the Netherlands Foundation for Astronomical Research (ASTRON) and the Netherlands Foundation for Radio Astronomy (RZM), two organizations in which Blaauw has held key offices. The scientific program was planned in full consultation with Adri- aan Blaauw himself. Only section 5, "A profile of Adriaan Blaauw", was kept secret to him. The other four sections: Structure of star-forming regions, Stellar content of young groups, Evolution of massive stars, and Extragalactic perspective on star formation, each represent an im- portant aspect of the overall theme of the Symposium. The program in- cluded 6 major review papers, 18 invited papers, 17 contributed papers, some of which were given as posters, and ample time for discussion.

Adriaan Blaauw; Emeritus Professor of Astronomy at the Universities of Groningen and Leiden, former Directo.r of the Kapteyn Laboratory and of the European Southern Observatory, celebrated his 70th anniversary on 12 April 1984. To mark this event, an international Symposium was con- vened on the subject "Birth and Evolution of Massive Stars and Stellar Groups", a subject which has played the leading role in Blaauw's scien- tific research. The present volume contains the Scientific Proceedings of that Symposium. The meeting was organized by a Committee consisting of: W.H.W.M. Boland (Secretary), W.N. Brouw, W.B. Burton, E.P.J. van den Heuvel, H. van der Laan and H. van Woerden (Chairman). Together, these six persons represented the Executive Committees of the Netherlands Foundation for Astronomical Research (ASTRON) and the Netherlands Foundation for Radio Astronomy (RZM), two organizations in which Blaauw has held key offices. The scientific program was planned in full consultation with Adri- aan Blaauw himself. Only section 5, "A profile of Adriaan Blaauw", was kept secret to him. The other four sections: Structure of star-forming regions, Stellar content of young groups, Evolution of massive stars, and Extragalactic perspective on star formation, each represent an im- portant aspect of the overall theme of the Symposium. The program in- cluded 6 major review papers, 18 invited papers, 17 contributed papers, some of which were given as posters, and ample time for discussion.