In a multivariate analysis, the concurrent introduction of novel PI(s) (32 p) and/or different NA(s) (19 p) acted favorably until the 9th month of follow-up (P B/0.04), while genotypic mutations conferring NNRTI cross-resistance, usually associated with a broad resistance profile, predicted failure in all p (P B/0.001), and the response did not vary according to duration and type of prior therapy, and selected NNRTI.