Preface
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The Joint European and National Astronomical Meeting (JENAM99) 
of the European Astronomical Society and the 
French Astronomical Society was held in Toulouse in September 1999.
Nearly four hundred participants gathered during one week to attend
nine plenary conferences opening each day and to subsequently
work in a total of ten parallel sessions on a variety of topics
covering star formation, asteroseismology, dynamics of star clusters,
massive stars and the ISM, active galactic nuclei, astrophysical 
fluid dynamics, cosmic microwave background anisotropies,
neutrinos in astrophysics, very high energy and gravitational wave 
astrophysics.

The present volume constitutes the proceedings of the two day session
on "The Interplay between Massive Stars and the ISM".
The aim of this session was to gather specialists from different fields
which allow to contribute to a consistent picture of the phenomena 
governing the multiple and complex interactions between these two
important constituents of galaxies. The main topics addressed were:
the stellar content and physics of massive star-forming regions, 
chemical enrichment by massive stars, and 
the dynamical impact of star formation on the ISM.

The session was very well attended both by participants fully
"dedicated" to this subject as well as "interacting" visitors from
other parallel sessions, resulting in both lively and fruitful
presentations and discussions. Thanks to all participants who
contributed to this success.

We are grateful for the help received from the Scientific Organising 
Committee (SOC) of our session which consisted of
Federico Ferrini (Pisa), Rosa Gonzalez-Delgado (Granada, co-chair), 
Mohammad Heydari-Malayeri (Paris), Dieter Lutz (Munich), Andre Maeder 
(Switzerland), Daniel Schaerer (Toulouse, co-chair) and Roberto 
Terlevich (Cambridge).
We would also like to thank Livia Origlia, Cesar Esteban and Nikos 
Prantzos for the work as chairpersons. Last but not least the JENAM99 SOC
and the local organisers, chaired by Sylvie Vauclair, are thanked
for all their work.
These proceedings have been possible through partial support from 
the JENAM99 LOC and an INTAS grant to DS.

Daniel Schaerer and Rosa Gonzalez Delgado

Toulouse and Granada, january 2000