An analysis of the compatability of ellipsometry conventions with the Mueller-Stokes calculus has shown that for the two approaches to be consist~ ent, modifications to the 1968 Nebraska ellipsometry conventions are neces~ sary. A sign convention is proposed which specifies the ellipticity angle and the fourth Stokes parameter to be positive when the tip of the instantaneous electric-field vector describes a right~handed helix in space. Polarization of this type will be designa"ted as right-handed and represented by a point on the · northern half of the Poincare sphere. The consequences of using this conven-.