Do stops slow down electroweak bubble walls?

We compute the wall velocity in the MSSM. We therefore generalize the SM equations of motion for bubble walls moving through a hot plasma at the electroweak phase transition and calculate the friction terms which describe the viscosity of the plasma. We give the general expressions and apply them to a simple model where stops, tops and W bosons contribute to the friction, In a wide range of parameters including those which fulfil the requirements of baryogenesis we find a wall velocity of order nu (omega) approximate to 10(-2) much below the SM value. (C) 2001 Published by Elsevier Science B.V.