Observations and theory suggest that clumping due to instability
 is important in the stellar wind of early-type stars (O, B, WR, LBV).
 Infrared photometry in the 60-200 mum range will allow us to study
 clumping in regions of the wind that cannot be reached at other
 wavelengths. They thus perfectly supplement H alpha and radio data,
 giving a complete overview of the radius dependence of clumping.
 This will constrain current theoretical predictions. Furthermore,
 clumping confuses our interpretation of H alpha and radio data in
 terms of mass loss rates. If these rates are wrong, much of massive
 star evolution will need to be revised. Quantitative data on clumping
 in the infrared wavelength range are therefore urgently required.