The  molecular  complex  Cepheus  A/B presents within an area of a few
square  degrees  a  full  palette  of  molecular  clouds  ranging  from
photodominated    regions  (PDRs)  heated by the stars from the Cep OB3
association,  to  quiescent  molecular  clouds.  Site of star formation
activity,  it  is  one  of  the  clearest examples of `contagious' star
formation.  Its  relatively  small  distance (700 - 800 pc) allows high
spatial  resolution  observations  and extinction measurements via star
counts.  Its  location  (l= 110 deg, b= 2.5 deg) far outside the bright
Molecular Ring and almost free of background contamination, makes it an
ideal  target  for  comparing  in  different  types  of clouds the dust
distributions with the CO and atomic C and H distributions.
 We propose to make a coordinated CO-FIR emission survey of a 1.5 deg x
1  deg area extending from the S155 HII region to the Cep A, B, F and E
molecular clouds. The entire area has already bean mapped in 12CO (1-0)
with  the  CFA  1.2  m telescope. We plan to re-observe it in the  12CO
(2-1)  and  13CO  ines  with  the  IRAM 30-m telescope. We also plan to
search for embedded sources at the interface of S155 with the molecular
cloud, around Cep B, using ISOCAM, and to map the CII 158 micron-m line
emission in the same interface region. The aim of this multi-wavelength
survey is to study the energy balance, to characterise the gas and dust
properties  in  the different clouds, and to estimate the molecular gas
mass  via  different tracers (12CO, 13CO, dust extinction, thermal dust
emission...).  The  ISO  data, which at long wavelength will complement
the IRAS data, will be crucial in this investigation.
 The  Cepheus molecular complex, observed at a distance of 3 Mpc, would
have  an  angular  size  of  4  arcsec, comparable to that of the Giant
Molecular  Associations'  observed  in  nearby  galaxies  with  mm-wave
interferometers   (e.g. IC342, Downes et al. 1992). Our study will help
interpreting these observations.