Clumping in stellar winds and interiors

The uncertain clumping properties pose a major problem for the quantitative analysis and the modelling of hot star winds. New results suggest that also the outer envelopes of massive stars may be affected by clumping, with important consequences for their observable radii and ionising properties. In this talk I will discuss how clumping is incorporated in stellar interior and wind/atmosphere models, how current theoretical results compare with observations, and what we can learn from a combination of stellar interior models and winds.