As? footnote, the error in survival:::untangle.specials is that it assumed that if attr(myterms, 'specials')[['strata']] was = to 4, then one could use myterms[-4] to remove the strata term.?? Not so.?? In the model? y ~? x1 + x2 + strata(x3)? the attritube will be 4 -- the response counts --- but to remove it I need to use [-3] since the response does not count in [.terms or drop.terms. Is this an inconsistency that should be documented and/or repaired??? What would break if we did???? I don't know.? By chance, all the usages in the survival package happened after a call to delete.response so it would be immune to such a change. Terry T. [[alternative HTML version deleted]]